I don't really agree that the lines need to be shorter - after all, this is a Norvel 061 with about 3 times the power of a traditional 1/2a trainer. Even in a decent breeze, 42' lines should be fine.

Theres lots of good advice here, but I suspect the 31% CG might've been a major part of the problem. I certainly wouldn't shorten the lines without first trying it with a more forward CG.