Soon I'll be trying a tonneau/duster without the windjammer. I'll be able to try with and w/o the freedom top panels as that will be my roof solution vs a bikini. It will probably be 2-3 weeks, though, but I'll report back with my experience...
I had one with the Bimini top with the zip down rear window behind the driver's seat and toneu cover I bought from extreme terrian didn't have any exhaust fumes only issue was when it rained and the jeep was sitting a puddle of water would gather on the Bimini top .I solved the problem by putting a pvc pipe in the cup holder with a tennis ball on the other end of the pipe and putting it against the ceiling making a tee pee look but no more water