I can't tell from photos in the other threads if people have done this, but be aware that a Kirkey seat needs a back brace. This precludes a sliding seat unless you have some sort of adjustable back brace to the harness bar.
I've got some Kirkey circle track seats in my 7. I also had one in my MR2 (RIP) that saved my butt (and the rest of me) from serious damage in a high speed impact (ouchie.) Note that with the high sides on them, getting in and out in an Elise would be quite technically challenging. Maybe with the top off it wouldn't be too bad, but otherwise, without hacking the sides off the seat, I think getting in and out would be beyond most of us.
Use of any Kirkey seat will require back bracing, a custom mounting solution, custom harness attachment points, and modification of the seats themselves to fit into the tapered tub. If you're a skilled fabricator, just pick the seat that fits your body and your safety needs and build around that. If you aren't able to do all of that yourself or able to pay someone else to do it you won't be able to make a Kirkey seat work safely.
My Elise is open cockpit so ingress and egress isn't too difficult. With a windshield and a fixed steering wheel, quickly exiting the car in an emergency might be difficult. I planned my roll cage so I could get out of the top or the driver's side depending on which side up.