I have an early effort of what you spoke Freaky... Gave the front end (XL350) to Tony T recently. yes the 500/4 was made to fit in the 125 frame, was to flimsy so rebuilt with hybrid 550/4 Sl125 mix .both were solos.... and truly awful.... and a prick to make a set of headers and pipe! Those days seem to be over now for me so try some ideas yourself , it occansionly is worth the pain. Tim