Do I have enough space for these

[Joe X]

I'm planning on getting 2 Fi ssd 15s and what to know if I have enough space for them. If not would the 12s be better suited for that amount of space? My dimensions are 15Hx34.5Wx28.5D

After trying your dims and setting displacements for the subs and a port with enough slot port area I get about 4.4 cubic feet net total or about 2.2 net per driver.

That's way below the 3 net per driver recommended for the ssd 15" and too low for almost any 15", IMO higher end 12s is the way to go unless you found/decided to use quite a bit more space.