I would say no. A 6' wide enclosed is probably well under 6 feet inside to inside, and you won't be able to get out of the SxS if you drive it in. You'll have to push or winch it in which is a pain, and that's even if it fits.
Most people consider a 7' wide enclosed to be the minimum for a SxS, and even that is tight.
We got an 8.5' wide for our enclosed, I would never want anything more narrow even for our Maverick Sport (also 64" wide like your DS). For an open trailer they don't have to be nearly as wide to be comfortable since you have so much room.
I would get one 14' long, even for a 2 seat X3. That way you can properly place it on the trailer for good tongue weight. We use our 14' open trailer for a 2 seat X3 and again, I wouldn't go shorter.
Just because something technically will work doesn't make it safe or a pleasant experience. What is your tow vehicle?