A couple options
I put the system in when building mine that installs the actuator under the floor, and uses a modified/different weldment. I love it, and it works great. I have my control switches on my MAC grip, and never have to take my hand off the stick. Another RV-4 guy on here, "SMRacer" installed electrics on his already built -4 with the actuator mounted vertically onto the R/H side frame below the roll bar, similar to the RV-8 set-up. I believe it may be a simpler way to do retrofit. He may chime in and have his 2 cents.