Don Noon

Maybe the player's ear adapts. That's a lot of added mass to the bridge, so I wouldn't be surprised if it did something tonally that doesn't change much. Then again, steel string guitars intentionally have massive bridges, and maybe it's not a big deal.

There are different ways to approach engineering and invention. One can swoop in with a bold, radical idea that "should be better". Everything on a violin vibrates, so any change in form or structure will have an effect on sound and/or feel in playing. If you cherry-pick the best of the earlier successes of the old craftsman and use that as the ultimate standard, anything different starts out with a serious handicap. A more complete engineering approach would be to find out how everything works and why certain instruments are preferred, and then try to more consistently make instruments like that... perhaps with subtile tweaks in attempts at "improvements". There's always the issue of experimenter (or inventor) bias when trying to determine if something is an improvement or not, as there is no objective, measurable way to get an answer.

Yarrrggh! "Fiddle tunes" with a music stand! What they are trying to play is the sort of music I mostly listen to, but certainly not THAT!

... you can't tune a fish. Sorry, it just had to be said. The good thing about taptones is that it's fairly quick and easy to get them and log them into a notebook (sorry, today it's spreadsheet). Then, after accumulating decades of data, you can analyze them and perform correlations, and discover that it's all pretty meaningless. At best, you can see that ones that were extremely thick had high taptones and sounded a certain way, and ones that were extremely thin had lower taptones and sounded a different way... but you didn't need the taptones to tell you that. If you are hoping for something to predict good vs. bad sound, taptones ain't it. And I can't imagine any reason why a "golden ratio" for anything would do it either.

Some of us do. The rest just think they do (but that can apply to almost everyone, not just engineers).

I have tried it, and the burnisher/scraper slide a bit easier against each other. But I don't see it as necessary, and don't bother with it.

It's far better than many over here.

and clean the lubricant off of the scraper before touching the wood.

If you set the body length, arch height, fingerboard projection, saddle height, and bridge position and height, then the total string angle is whatever it is. I do those other things, and don't do anything too abnormal, so the total string angle comes out about the same (normal) every time. (edit: oops, I neglected overstand, which also affects string angle). If I did setups on short body / high arching violins or other oddities, I would probably look at total string angle. I don't know of any theory that can determine an "ideal" string angle, other than what seems to work best in practice.

I don't measure the angles. Eyeball.

If cost is the concern, you can get a 1/4" x 4" carbide rod for $15 on Amazon or eBay.

I wouldn't expect marring of a carbide burnisher unless you are using it on carbide or diamond scrapers (you wouldn't be able to turn an edge on them, anyway).

Those drill bits might also be sourced from China, or Romania, or similar low-priced (questionable quality) supplier. With similar results to your "HSS" rod.

A much better deal than a banana duct taped to a wall, and for about the same price.

That description is very suspect, using HSS and carbide interchangeably, and no specification of hardness. Apparently from China on eBay (https://www.ebay.com/itm/376614571652), where there's not much certainty of getting what you think it is. From the nicks on the bar in the photo, my best guess is that that "HSS" bar is too soft, if it is indeed any kind of HSS.