it might be that he doesn't need that strong of a bit on the trails. Also, this is just my personal preference, but I don't like riding with a shank bit because I've seen a horse get it caught in a tree. Not a fun day.
If you asked your horse to go, which gait would he choose? Just like in an arena? Sounds like he perfers the lope than any other gait. I personally would be alright with my horse loping up the hill, but that's me. I guess it's on personal preference on what you like your horse to do.
Satrider, I hope you were alright, but that could have happened at any gait.