Don’t know RV-4 and don’t know how significant the mistake is, I did something similar to your mistakes.

Clean it and around it first to have some cleaner wood in these areas.
The way I reinforce the LG and wing plates is by adding tri stocks or other harder then balsa wood with 30 min epoxy this time, now cover that with fiberglass and epoxy to the fuse about 1 inch extra to the sides, this way it holds better to the fuselage.

Alex