Raskin,
According to their website, gokartsusa.com has the TrailMaster in stock; $899 w/ free shipping. Familygokarts.com has it listed for preorder at $749.98 w/ free shipping. I've considered preordering one, but I'd rather have the Monster Moto. I like that the MM has real brakes. As a retired welder, I'd rather fabricate rear suspension on the MM than attempt to upgrade the brakes on the TM. The MM's frame looks more stout, also. When you consider that a 49cc Yamaha Zuma scooter is $2,599 and a 49cc Honda Ruckus is $2,699, $900 for one of these big bikes doesn't seem too bad.
On the CT100U, the seat is already at the back of the frame. I could fabricate something to move the seat back, but then I'd be doing wheelies sitting still. I could stretch the frame, if I wanted to. I think I'll just leave it as is; ride it occasionally for S&G; get something larger. I've thought about buying an American Flyer 215 frame and doing a full suspension mod on it, but I have too many things I need to do, for now. I think I will buy the MM-B212. I hope Walmart will carry it. If so, I'll price check it every day; they have the MM-B80 on sale, occasionally.