Bill,
Here is the link to the rules for VSC. They specify the 50% rule.
The AMA says you can change the rules for your contest if you put out advanced notice, so here it is.
The AMA changed the rules AT the Nats, so I don't see where this is a problem.
If you use an ARC wing from Bobby, I think it's OK to use an ARC wing from an ARC. It wouldn't bother me. We've been using sheeted foam wings since '66, George A. was ED and said it was within the BOM rules.
Chris...