Interesting! I've only made one double-sided quilt and I made both sides the same size. I just made sure to match the edges of the sides up and then machine-basted them together around the edges. Then I just FMQ'd the whole thing with loop-de-loops and called it a day. I ran into problems where too many seams intersected and had to sort of jig and jag around those, but otherwise I didn't have trouble with puckers or anything else.
BUT...both sides were foundation-pieced crazy quilts and maybe all that extra fabric makes a big difference in keeping things the correct size/shape(??). It was kind of a failed experiment anyway, it ended up so heavy I just keep it over a chair, it's not really comfy to sit under, and I didn't even put batting in it. Next time I do crazy quilts like this I won't do double-sided. Oh well. I sure did use up a LOT of scraps though! LOL