Hmm, maybe you're thinking of an older model of the Ultimate. I'm running GP5000 28s with at least 5 mm clearance everywhere. A quick google tells me the 2012 supersix evo s 695 g and that the Ultimate CF SLX is 780 g. Assuming those numbers are both for the same size frame, that's pretty impressive.If you can squeeze on a 56 with a bit of stem and seat post adjustment, there is a cool looking old SuperSix Evo on Yahoo Auctions. This frame is probably lighter than your Ultimate. It comes with the seat post, but doesn't look like a special one that can't be replaced and screws up your bike fit. Like your Ultimate, this will probably only take 25s.