Another good reason to use a tripod, I guess. Nevertheless, it seems you've already had a go at this, so how did the prints turn out? Just try a few rolls and check out the results. Then if you need to change your technique you'll know what you need to do. For what it's worth, I do the same as Ben with my 645. Haven't noticed any problem so far.

If nothing else, a few lifts and you'll have done your biceps a world of good.