If you are unable to comfortably seat the fully loaded magazine with the slide closed, then load one round down.

I have never had an issue with either the 8 round CMC Power Mags or the 8 round Wilson 47D or Elite model either.

That said, a great many of the experts have suggested using the 7 round Wilson 47 as the highest reliability magazine for the 1911. On the other hand, Wilson now makes the Vickers ETM-V, which is an 8 round magazine, and it is supposedly the next big thing.

Personally, I would say stay with CMC or Wilson in the 1911 and you should be ok.

I do not know who makes the mags S&W supplies (lowest bidder, perhaps?), but like the S&W's FLGR they insist on putting in their 1911s, I would "opt out" and get high quality mags (and standard GI guide rod with recoil spring plug).