Prius C Brackets for Aftermarket Seats?

Hello,
So, I've had my C for 1 week now and do appreciate the superior engineering and design!
While I did notice that the stock seats do have decent back support it's comfort is good for about an hour driving before my back starts to complain.

So, I already have a pair of Recaro sport seats pulled from another stock car - Mitsubishi Evolution VIII to be specific. They're just siting in the garage. But, when I search for a aftermarket seat brackets I only see options for Prius lift backs and nothing for Prius C's.

Anyone know if Prius C seat bracket is compatible w/ Prius or a vendor who carries a bracket for C's?
thanks!

 

Racing Seat Brackets / 1 Pair / Fits Sparco & WR Seats
Application: TOYOTA YARIS 2007
MSRP: 120.00
Item Number: 954-119-101

getting warmer

 

After looking around I don't see an aftermarket brackets for C specific. Yaris unit may or may not fit...
I'll make my own bracket w/ a pair of rectangle steel tubes. I just did some measurement and looks not too hard.
Stock mounting points on the floor are mostly flat and parallel front to back.
I'll start this mod soon enough, first ordering some steel tubes.

My back is getting sore from the stock seat...