Honestly I may look for a different gunsmith for this build. One who has built something like this before and isn't saying it won't shoot from the get go, because if you tell him to build it anyway and for some reason it doesn't shoot, all your getting is a I told you so.
I have a similar setup, not 338 edge, a 308, with a 28" SS bbl 1.25 to .9" at the muzzle straight taper. Bedded with devcon in an hs precision "psv" series stock and I set an LR f-t/r national record with it, so I'd say it works ok.
mine also has the first 2" of barrel beyond the recoil lug bedded.