As this thread, ultralights in America are dead. There are a few building them, legal eagle and belite but that's about it. Even a quicksilver with a 447 is over the 254 lbs limit. But it does look like an ultralight so no one says anything.
You will find trying to meet the par 103 regs in the USA is going to be tough using anything but a single cylinder engine. Ultralight engines are as dead as the ultralight, in the USA with our regs the way they are.


Tony