A lot of the Honda peeps use 'RO' type seat rails from Bride to work with Recaros. They are available by the tonne on Yahoo japan but I'd imagine the done thing on a K11 would be to modify the existing frames due to it being the cheaper option?
I actually bought over a set of 'FO' type Bride rails to go with my Sparco Evo's. The only thing required to make those fit is to use a set of Sparco seat mounting frames, as the ones supplied by Bride are for the narrower Bride seat.