The subject is a 320? Probably an updraft carb, so RV-7 or 8 horizontal induction ductwork isn't directly applicable. And it might be difficult to duplicate the RV-7-8 duct due to the shape of the RV-4 cowl.
I have heard of RV-4 builders happily ducting to the carb from a port in the rear baffle wall. There will probably be an air temperature rise between the cowl intake and the duct intake, which would result in a small HP loss. I've measured 15-16 degrees F in some personal experiments, but the parallel valve 320 may not heat it so much. On the plus side, conversion of dynamic to static should be good (MP gain), the cowl would be easy to R&R, fabrication would be simple, and you would eliminate the form drag of a pitot-type inlet.