Short jackets weren't odd. Confederate veteran Mr. G.H. Baskette says jackets too short was pretty standard...
Illustrations by Confederate veterans:
Perhaps it would just be easier to hike up the trousers with suspenders, or perhaps a new pair with the higher "rise" on the body if necessary. Or just let the shirt-tail fly some as noted.
I have to ask, are you wearing your trousers where they were meant to be? Should be up to your naval, that's the natural waist and were period trousers should be worn. And that's about where a properly made RD shell jacket should stop. It really looks silly if you try it on with modern jeans/pants that we wear much lower these days.