HoGo

Yes, that's the only type of form I've used.

I use outside form for my mandolins similar to what BF posted above (BTW, the holes at the end of the points are there to allow for glue squeeze out, I made my new from that way after some "experience"). I always put one rib in a bit longer and slightly chamfer the other one so they meet with a tight flat butt joint, then I fit the block so it goes all the way in without opening the tip. No problem at all to get almost zero glue at the meeting point and also a joint that appears like built on outside form with bout rib butted to C rib. The OP violin doesn't show that butt joint at all even in the one example where one rib overlaps in straight line. IMO, the other rib was just slightly chamfgered to meet at the tip in the form.

No one knows what the original arching was. these instrument have been repaired, patched and sandbagged numerous times and many underwent so much thinning and deformation under string tension that one can hardly estimate what they looked like when new. I once compared side views of du Diable violin taken ~100 years apart (and posted here on MN) and there is noticeable difference in arch flatness under bridge and bulding near ends.

I see the template be 345mm which is without ribs and overhang which is on generic models 1.3+2.5mm that would add 7.6 mm to final length that agrees with approx. 353 mm measurement of the larger template I see in your pic. If you traced the larger template with additional 3 mm washer than you ened up with not only longer fiddle but also wider and with HUGE corners and smallish C bouts space between them. The size (length) of the wooden form below the template appears way smaller than the template to me. How did you come up with that?

I try to fill with matched and fitted piece of wood whenever even slightly possible. I don't think I've used filler in my life on instrument. I use thicker filler varnish only over glued cracks when the crack edges miss tiny bit of wood.

It's common technique on guitars and I've used it on mandolins (with oil and spirit varnishes). There's always possibility that delicate finish will get slightly damaged but so far I at worst got some haze that either lost after day of drying or after some french polishing. On most guitar lacquers you can steam out quite safely, just never touch the finish dry. And always lightly. I believe your dents will go completely away as they are just pressure marks and wood is bare and allows steam do it's job. Very light sanding or scraping should get you back to clean surface. Here is article that covers it: https://www.frets.com/pages/vb7i32xw/Steaming-Out-Dents.php

I use ordinary clothes iron or soldering iron to steam out dents. Wet paper towel folded in half and gently apply tip of iron. The paper may burn a bit on surface but it won't affect wood (I mostly use it on dents on damaged finished instruments and most varnishes or lacquers can handle it if you keep the towel wet and use only second-long touches) repeat as many times as necessary moving the towel to fresh wet spot after each touch. New wood responds well to this. Don't do this anywhere near centerjoint if you don't want to unglue it.

We didn't see the outside, the edges may be overly bulky not rounded and even not trimmed for uniform overhang. Many makers leave carving the final depth of channeling towards end of carving. That may reduce the weigth by few grams.

I use small wedge between the ends of pillars to align the crack so both inside and outside will close at the same time. BUt re-humidifying the plate is good idea before handling the crack.

Perhaps better heat treating can help some of those blades. Quenching ordinary carbon steel is not a rocket science.

Was that photograph adjusted for distortion? On most posters and similar pictures the scroll pics were taken from relatively short distance which exaggerates size of the second and especially third turn. When I compared resized pictures with caliper measured numbers there were too large differences inflating towards the eye. Enough to not be usable for the second and third turns. With enough fractions of unit and enough circles connected you can design Ferrari or cathedral. I agree that the original design was most likely carried out with series of circles I wouldn't be so quick at suggesting their exact centers and diameters. The scrolls are often very worn and even if we assume the original drawing was perfect, the cut out template (if they used it) was likely slightly "smoothed" by cutting out, the marked outline was likely not cut exactly to line and smoothed with scrapers or glass by eye, then the final cuts of turns were likely not exact replicas of original intention as well. So this accumulated error makes exact reconstruction of scroll geometry impossible just from photographs. Something can be found on the paper/parchment drawings from Strad's workshop but there are too few of those. You'd need to reconstruct full unworn outline and compare many of those but preferrably not working from photographs that introduce errors of their own.

They appear to be carved in... right through the knot on the bass side of top! Cool.

MY real world experience is from (archtop) mandolins so it may be slightly different from violins... I always do final shaping on white instrument with strings tuned soI can play and feel the shape of neck in real action. I found that reshaping the main "shaft" of neck doesn't do much if anything at all (while sytaying within physical stiffness of healthy neck) but I noticed in few cases that reshaping of the heel curve (deepening it just slightly) made some difference especially in case when there was more wood than necessary and reshaping it more to "normal" so player can reach up the neck with thumb hooked at heel comfortably. In these cases the tone "opened" a bit. It's hard to describe but perhaps better response and richer tone was the result.

Did you do the back repair as well? Looks like it was bitten by Dracula . The two visible dots in the top and hole just opposite on back. The bass bar looks quite low with squarish crossection.

Looks like exposed pin knot. The first mandolin I built has pin knot going all across one half of back mostly on the outside. No problem in tone or longevity after nearly 25 years.