What do either of those options gain me? I've had a Burley and really didn't like the BB setup, tried modifying a cannondale mtb tandem but couldn't get good positioning on it being the wrong size, but either I'm looking at 1000.00 or more, c-dale seem to be 1200+ most times. Both are going to be old with unknown levels of use vs new frameset and mostly lighter used parts fitted out with new parts as needed. Can you explain why they would be better?