I think that you can convert an "R/S" seat to 1300c, but I'm not sure about the other way around. There is modification involved for sure.
Depending on what seat mod you are wanting BadX to do, I may be able to help you mod your own. I will be re-shaping the foam on my 1800c seat to smooth out the bottom to try & alleviate the "butt-burn". I put about 200 miles on the stock 1800c seat today & I know that I definitely need to reshape the foam. I plan to try it myself & if I screw it up, I'll send it to BadX & have him do the memory foam mod.
I don't want to take away from any of BadX's business, as he does a phenominal job (speaking from experience as a satisfied customer), but I want to take a stab at it first & try to save some $$$. 8)
Anyway, if I am successful, maybe we could re-shape your stock seat & make it comfy too.
Just a thought...