Acoustic Guitar Construction

what do most of you guys use for radiuses on the top braces

I mostly use 28' for steal string guitars tops.

All our KMG kits are supplied with 40' pre-contoured soundboard bracing -- the internet standard has become 28' which has been inaccurately repeated as the Martin standard. Martin braces are pre-contoured at 52' merely to prevent a concave appearance. As one might expect the majority of the sound-board dome comes from the pull/tension of the strings. The main purpose of a dome sound-board is to increase the area of the plate --so if the humidity drops and the sound-board shrinks it will tend to flatten out before it cracks.

Do all braces get radiused on the top

X braces and tone bars (bass bars) The shoulder brace generally is flat with a tiny slope at the out edges to blend with the upper bout end of the rim, which should be fairly flat to accommodate the "flat" slope of the fingerboard extension.

I used 40' for my bass guitar, top and back. I use 28' mainly because I am building guitars the way I was taught by Rick Davis. I have no problem with 40'. I am planning on making a 00 12 fret to the body. On that guitar I plan to follow Ken's method to obtain the correct geometry.