How many times has a dec guy come across a custom made, marginally legal bow in the field?
I wouldn't want to be his first.

If I was the OP I would call dec or similar agency,
Tell them you want to keep it legal, just what he can do in case he gets approached by dec, ask them what they would look for.maybe all he needs is a receipt from a shop indicating its a 35# even if a shop charges for such, may be worth it..
Something I would consider.