I started to reply to this thread yesterday but don't see my response this morning so I must have gotten sidetracked.
We use a larger back window on the Speedster as a standard and can make it even bigger on request. The one pictured on Lane's old car is a little larger than stock and is much nicer as a zip-out otherwise it tends to crease the material when folded.
Speedster high bow is our standard.
Our Spyder top stores in the nose of the car, at full width. It's a tight fit but the header bow just goes in. With a little work one could make the rear window of a Spyder removable, or make a bimini style top like pictured, HOWEVER, I would highly recommend some aero testing before this was done. The aero on a Spyder is a bit different than a speedster and the way the air comes off the windshield and doe sa 180 is much more severe on a Spyder, so I have a feeling that you'd have a few issues that are not present on a Speedster. I know that may sound weird, but I've done a ton of telemetry and wind testing on both over the years.
Seat height, yes the floor of our new chassis sits lower than previous cars. It still can be modified for even more room, but Ive yet to find that necessary.
Hardtops are a one off thing, individually fit, and while we can do them they are very expensive and time consuming. I don't advertise them, or even offer them "officially".