I have a stock type QH mare who is built downhill and naturally is heavy on the forehand because of her conformation. Honestly, she is built like a tank. She has been a pretty nice trail horse other than she just plows her front end into the ground if you let her go on a loose rein. Obviously going down hills is the worst. I can get her to come together and lift herself up IF I establish contact and push her into it - however this gets old for both of us especially if we are on a longer ride. I have been working on increasing her fitness and in the arena, she is very capable of getting off the forehand for an hour or more at a time (but again with contact).
I do work with her in the arena and on the trail - lots of transitions (w/t/c), lots of yields off my leg, circles that kind of thing but she has to have rein contact to convince her that she can in fact use her hind end. I also do some in hand work with her to increase her strength and fitness.
I know some of my problems do stem from her conformation. If you watch her move in the pasture - she naturally is just heavy on the front end. When I bought her, she was 3 and I was somewhat hoping she would grow out of some of it but now she is 8 and well, she didn’t. (I bought her because she has a great brain, is willing, sweet and solid on the trail (even at 3) even though she didn’t have the best conformation I had ever seen) She is the horse I pull out when I want an easy no thrills type ride.