I think you will be OK with the 15 degree swivels in that position. I added 15 degree fixed holders in that position (actually by accident because I'd thought they were all 15's) and this past summer I used a swivel inserts with bent butt rods for giant fishing. The up and down angle does shift as the fish moves, but it still works pretty OK, even with a huge fish.
But this winter I'm adding a 0 degree holder in the position in the pic below. It's basically as far aft as possible, just ahead of the divider. It's right over the galvanic isolator so that's being relocated. I also like fighting big fish from the aft corner which will hopefully help keep clear of the motors and also allow the fish to drag me backwards when it's a big one. This summer I had a cow drag me over a mile with 40lbs of drag!