Add the gussets at the lower corners of the firewall/forward fuselage area ala the RV-8.
Dave P is right...you will need to maintain, at a minimum, the same relationship of the wheel axles to the wing LE, and preferably 2 inches forward of that per Rocket guys Mark F and Vince F to help prevent nose-overs. Because of the longer legs of the RV-4, you will need to change the socket geometry at the engine mount (spread them out). Since you're going to beef up the mount, this will be an easy change...just get the geometry right before welding.
As you know from our last email exchange, I have a full set of Rocket drawings. I could be willing to part with them. Let me know if you're interested, and we can work out a deal.
Sounds like a cool project. Good luck with it and keep us in the loop as you make progress.