Some of the links on this forum allow SMF, at no cost to you, to earn a small commission when you click through and make a purchase. Let me know if you have any questions about this.
"Large" is sort of subjective to what's common on the shelves everyday at your supplier but I usually run an average of 20 prime packers when I cook them for a big event and the packers 15+ pounds trimmed with a carving mark taken off the end of the flat grain are going to occupy 22" or more of real estate when they first hit the grids before any shrinkage.
You should be fine, short of buying a Bullzilla Packer. Besides, there is no reason turning the Flat end under a bit will hurt. Not to mention, trimming a couple of inches wide piece, makes a great Pit masters snack, a couple of hours in...JJ