I have the safari top, deck cover, and wrap around jammer on mine. Yes it reduces the cab room but not too bad. I have my seat all the way back and leaning back some and I have pleanty of leg room @ 6'2".
You still have some floor space behind the front seat for a mini tool box. If you have the safari top you will get better coverage from keeping rain out of the cab but my deck cover is for running with the soft top hardware in place, even thought I took it out.
There are a couple spots where the top does not meet the jammer flush but if I really wanted to I could put a snap or 2 on the top and jammer to seal it a bit better. Safari top helps keep the rain from coming in the back when driving or sitting better than just the bikini top.
I have taken running it year round now over my soft top. I like the smaller cab feel especially in winter. Since my heater don't work the smaller area gets warm from the engine and transmission heat...
You can kind of see how the sides are on my jammer here: