i can attest to a few things since i kind of saw jack a minute at my gym the other night. his chest depth and back thickness do actually make his arms look smaller than they are. i would put them at 22 or 23. realistically. but at 290 lbs he is a very thick dude. also from what i have read he started all this stuff as a powerlifter so he has a thick base to begin with. look at johnnie jackson. same type of issue. i would put his measurements around:
arms - 22, 23
neck - 26-27
calves - 20-21
penis - 1.5
LOL, sorry jack. just bustin. figured i would put something in for true adonis to find interest in.
btw, if you get a chance, check out adonis's pics. not a single shoulder bump at all. no definition between biceps and triceps. and he is as smooth as a baby's ass. thank god he doesnt have to worry about things like, cuts, definition, muscle tone, low bodyfat.
anyway, thought i would just give my perspective.