i have a b-square base on a 10" Armour Alloy .44, and used 3 Millet rings on it to hold a 2x Leupold...so far it has held up fine with no slipping. I also have some b-square rings on a 14" .223, but using a weaver base, no problems there either.
As for the Weaver 2x28, i have one on a 8" smith .357 mag, & another on a 9" .32 H&R mag contender...no complaints there. In fact, the Weaver & the Bauch & Lomb are my favorite 2 2X scopes, i prefer the 28mm objective over the smaller 20/22mm lenses used by most companies.