Definitely looks like you're sitting too far forward and/or the chair is a couple/few inches too short for you. A couple fingers cushion clearance behind your calves is all you need, generally speaking.

If that black bit behind your left shoulder is the top of the backrest, I'd say that's WAY too high. T injuries can often feel pushed forward and uncomfortable not having their lats and traps free of the backrest. IMO the backrest shouldn't be higher than your injury level for a thoracic injury.

Can't tell if it's because you're too far forward but axle position looks too far back. The rule of thumb is you should be able to touch the hubs with your finger tips with your arms hanging relaxed.

Can't make out dump in this angle, but it looks shallow. I'd recommend 2.5-3" as a good place to start for a T10.

Is your newer Stimulite cushion contoured like the old Jay? It might should be, if not. Contoured cushion can help keep you in place, although if you're constantly sliding forward shearing injuries are a big concern to me, so addressing the other chair geometry issues comes first IMO.

There are a couple rehab places in my region I can visit to try chairs out. Maybe something like that near you too?

Either way, my priorities would be, were this me, in this order:

- MUCH lower back (~12" high from seat pan)
- Longer chair/move backrest farther rearward
- Experiment with more dump
- Experiment with axle position
- Contoured cushion

Tough part is, all these changes will impact each other (wheelchair is a closed system), so taking them one at a time is important IMO. I think this order of operations is a good approach to managing this, but once you get to start tweaking axle position and dump, you'll most likely have to go back and make perfectory modifications to your back angle and height.