Old thread, but I finally got a set of the locking rail covers. They fit (are you sitting down?) tightly, with absolutely no wiggle or play. Shoot the gun as much as you like, and (be still my heart!) they don't move around. You actually get rock solid control of the foreend. The gun feels, well, like a $1700 gun ought to feel. Except for the junk trigger, of course, but that'll soon be history. Anyway, these panels are pricey but worth it, to me at least.
Thanks, Terra, but I'm really happy with these Ergos. I just passed my experience along for those like me who find the monolithic upper kinda clunky to begin with, and really tough to control when the covers move around. With tight covers it's much, much better. Come July (trigger time!) I'll have a trouble finding something to complain about. On the rifle, anyway. I can always find fault somewhere or other, any time.