Under String Radius Gauges

[Dr loomis]

Anyone here ever try out the under string radius gauges that matches the bridge radius to the fretboard radius? I have found limited info on them, only from Stewmac.com. How do you use these? I think you get a set of 8 different size gauges and you have to find out which gauge to use for your guitar neck. Do you match the gauge size you need to the 12th fret? I'm confused cause a lot of guitars have a compound radius that increases on the higher fret end of the neck. I think you just slide (the proper gauge between strings 3 & 4 and back under 1 & 2 and rest the gauge standing up on the 12th fret) then adjust each string saddle until the strings just touch or fit snug on top of the gauge. Correct me if I am wrong.

[Newc]

From what I get of the text at StewMac, you find your board radius on the board first (but not which fret), then whichever gauge matches the board, set the strings to match the top of that gauge.

It still does seem very vague, but then StewMac aren't the most up-to-date crew IMO. They're just a little too zealous for the Vintage Fender/Gibson/Martin specs and do everything they can to ignore modern specs (i.e. they only offer the R2 nut and short block with Floyds, like they're only going on narrow-nut Strats and never on a Les Paul (non-recessed) or 1 11/16" nut).