It would seem logical that the same N frame Smith uses in the model 29/629 .44 Magnum would be more than strong enough to handle the less powerful .45 Super cartridge. There seems to be a contradiction going on here.
Well the 625 was desined to pop out the 45 auto with good margin, and without some inherent design weekneeses over the 1911. There are no dynamic parts during firing (trigger excpetion), and the case wall is fully supported in the chamber. One of 1911's weeknesses when using 45 supers was the relatively week web layer that is exposed over the feed ramp which could rupture in a high pressure round like the 45 super, which is why special 45 super brass must be used for this load. And as Zen mentioned, the use of the heavier frame in the gun would certainly give you an appropriate level of enhanced strength. As a general rule of thumb, wheelguns can take more of a beating than a semiauto, just the nature of the beast. My personal load of 45 supers I use out of my custom built longlside is 8.5Gr or Power Pistol behind a 230gr TMJ-RN. With CCI Large Pistol Primers. Chronograph around 1150 to 2000 fps on a given day. If you want hotter, Texas ammo sells 230gr .45 super Exxpress ammo that chronoed out of my longslide at 1300 fps. The gun was modified for this, but I have to say I backed off even though everything looked fine. One other issue to consider, the higher pressure loads you want to run, require a long barrel to burn consistently, so stuffing one of those 45 supers into a 4" barrel is not going give you the powder burn or velocity you want. Need at least to use a 5", prefferable a 6" barrel to really get the potetential of the of the gun. I love the cartride, only load it up stiff when I'm going backpacking or hiking and then just convert back down to Mr. Moses orginial recipe.
SOme guy on another BB said .45 Super cracked a 625s cylinder and said only the unfluted versions were able to handle fullhouse .45 Super. I must admit I have shot a few boxes of .45 Super through all but one of my 625s with no problems, furthermore, Clark Custom will convert a 625 to shoot 460 Rowland which has even higher pressures.