So the question is, if I use a heart diffuser, would that lower the 24" difference from grate to fire basket?
If you put a shelf lower then I would suggest you'd need to monitor the temps at that level and adjust your air intake accordingly. I don't see why a good diffuser wouldn't allow that. The only other thing is the lower the shelf the less likely your meat is to be hanging around in a smokey environment. You will probably still get plenty smoke flavor from it tho, unless you like it SMOKEYYY.