If you're looking for an "egg-shaped" egg to fit into a standard garage, the Boler/clones (Scamp,
Love Bug, etc.) will have the best chance. That's because they utilize a dropped center floor to get headroom, and you instantly gain (or should I say
lose) about 6" that way.
The Trilliums and the Cloud/clones (Burro, U-haul) do not have a dropped center floor, so they are higher right off the bat.
Now, that said, you may be able to do tricks with bare rims, dollies, or the like; but I don't believe that any
Trillium or
Cloud clone will go into a 7' garage in stock form as some Boler/clones will.
Not even all
Boler clones will do this, but some of them will, especially the older ones. Even with a new
axle I believe you can keep the older ones low, if you are careful with your set-up (and there are some still rolling around with original axles that are still functioning).
So, still best to measure the exact trailer you are potentially purchasing, but know that you will stand your best chance with a Boler/clone. (I'm talking 13-footers here since you mentioned the
U-haul 13).
If you are considering "toaster shaped" trailers, then the Compact Jr./Campster/clones will easily make it into a 7' garage, because they have pop tops that give you the headroom when you are using them.
Raya