Most custom barrel makers recommend not going over 26" on a small shank....this would be total lengthen including any muzzle device.

I have a 28" bull contour on my 300WM small shank Stevens 200 (I know, I know, All Stevens are small shank) and with the APA Fat Bastard I'm over 30" However, bedding a few inches in front of the chamber relieves some of the stress on the small shank.