riding a different breed of horse and havin trouble

I have been riding at an all arabian barn for the past 4 years and have loved it. But unfortunitly it was just ggetting boring for me because it was all flat work, so i`ve recently started riding at a new place i`ve only ridin there twice but i`m having some diffculty with these horses gait at the trot and the fact that I used to ride in dressage saddles so the close contact jumping saddles are also giviung me difficulty.Tthe horse I ride is a quarter horse so I find the trot alot bouncier the the arabs. I try to keep sitting back with my heels down but this doesn`t seem to make much of a difference, has this problem ever happened to anyone and how did you get used to it.
Thanks!

He knows when you're happy
He knows when you're comfortable
He knows when you're confident
And he always knows when you have carrots.
~Author Unknown

I find it hard to adapt to a jumping saddle , comimg from a dressage background. I think you need more bend in your knee, more use of the thight and calf and get more impulsion from the trot so the horse will help you get up and out of the saddle.