I have two packs of 10 each and I always figured if I have to raise the TT more than two high then It's time to move or at least move it side to side to bring it closer to level. I just don't like the idea of having my TT higher than 2 high for safety reasons. I was always afraid of it rolling off the blocks, even chocks didn't seem too secure to me. I was unhooking in a rain storm once and the TT rolled forward and almost got my sons' foot had a bear of a time getting the tongue back up but I did and I have always been a little nervous of that ever since. live and learn I guess.