Have you at least sat in both the Sport and non-Sport versions?
A cockpit of 21"x38" on the non-sport is pretty good sized cockpit. Not sure how big you are but I am big and sturdy and have no problems getting in something that sized. I would be more concerned about the deck height and if you would be able to get your legs in once you sit down. If you have large, long, or poor flexibility in your legs you might have a problem but a cockpit of this sized for big paddlers might be as small as you can go. I can fit in slightly smaller cockpits lengthwise but I have to slide in feet first.
The advantage of a non-Sport cockpit for a larger person is you can better contact with the hull for control. This is not the preferred cockpit size for those little people out there but they work well for those of us who are larger and active.
On the larger cockpits rec/touring kayaks like the Sport you are trading control for ease of entry. Also having a bigger opening allows the potential for water to get in the kayak and spray skirts can implode from too much water pressure on them. So you are limiting yourself to slightly calmer waters.
Not sure what your leg problem is but there are things you can do to relieve pressure on your legs when you kayak. Again this comes down to spending sometime with a dealer, sitting in kayaks, taking them out for demo, etc.
A good fitting kayak is probably tighter then most people think it should be and probably not your first choice without some lessons or lots of butt time in different kayaks. Being big does limit your choices a lot.
Free Standing Boat Racks
Pull-Up Strap Handle Kit
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