Marcus, I have an early mono CAV and the cars have a direct lineage to KVA via GTD. Mine also doesn't have a dropped floor so its dimensions may not be as different as you might otherwise suspect.
I've also seen quite a few KVA adverts but there was nothing humble about them, they were terrific cars. The ones I saw (like my CAV) had inserts in front of the foot-wells that can be removed. On my car there is significant space in front of them.
I think I picked up about two inches with my seat arrangement. I'm right at 6ft. However, my car also has multiple location mounts for the pedal assembly resulting in plenty of room to scoot down. My car also had a bit of fore-aft seat adjustment (think airline seat). So in my car, there is a lot of space going forward in the foot-well. My suggestion would be to measure and mark your shoulder height in the seat and measure shoulder to cockpit roof distance and determine how much additional headroom you need. Then unbolt the seat and experiment with spacers and see of you can tilt it back enough to get the space you require. Even if you have to modify the seat, that would be far cheaper than dropping the pan. Given your size, when you're in the car, I suspect you pretty much compress any stuffing in the seats so I don't think removing anything there will get you any material benefit. I bet there are several KVA owners that have faced similar issues and come up with other solutions. As keep reminding myself when I'm fussing with the car, "it's a hobby they said, it's fun they said...".