I haven't tracked my RX-8 yet (plan to start next spring), but I was planning on using the CG-Lock seat belt lock:
http://www.cg-lock.com/index.html
Eventually I may replace the OEM seats, and Recaros were what I was most interested in. What model of Recaros did you get, and how did you hook them up? Do they sit a bit lower than OEM? I'm 6'3" and I'm concerned that with a helmet on, I'm not going to fit in my RX-8 so well (I have the power moon roof, which I didn't particularly want).