I'm sorry for posting then. I knew what was being discussed, I just wanted to point out that the two were different. Again, I apologize.
youre fine. i was correcting my prior post about the RD being a single backbone frame. i knew that the brat bike wasnt an RD, but the tank was. the OP was asking if the RD tank would fit an XS, i said "i dont think so", and then corrected myself. no biggie.