The main problem you'll encounter is that when the trim is activated, the pivot is in the center of the driveline. That means that the distance from exhaust elbow to transom will change by several inches as you adjust trim.
The way I got around it, I made a slip-joint with smooth 3" rad hose, with polished 3" stainless tube inside it, with no clamps. It's a tight fit dry, but I lubed it with silicone grease. I had 4-6" of overlap so not the slightest hint of a leak.
I used the same 3" ss tube to fab the tips, and formed a 30? elbow just inside the transom to have it incline up to the elbow. I double clamped a 12" piece of rad hose to that, slipped a straight piece of 3" ss into it, then clamped the tube to the elbow with a short piece of rad hose. The upper piece of rad hose will pivot a few degrees with trim.
Once I saw that it worked well, I added a "Y" to the ss tube, put a butterfly in 1 side, connected the other side to the oem exhaust pipe going to the mid drive. I control the butterfly with a 3/4 x 2" Bimba pneumatic cylinder, activated with manifold vacuum thru a dash switch.
