The spooking QH sounds like a nervous horse though, If I understand the
post correctly it is spooky only outside of its riding area. If possible
I would recommend to do a lot of circles, etc in an open area so that the
horse learns to think of the riders aids as its boundary instead of relying
on a fence. Then move to trail riding with a calm horse buddy along, and
try giving it extra contact (push it into the bit a little with your legs)
when it seems nervous of something - A lot of horses relax about scary
things if the rider takes charge in this way.
Cheers,
Teresa