This is all great info , here's a pic of the mod's on my Brain Taylor F4U-5N.
http://images.rcuniverse.com/gallery.../lg-229965.jpg
Another advantage of the -5 is the full scale cowl is about 19" longer so, you can mount the engine further forward thus reducing the amount of lead for balancing.
The cowl flaps had been lengthened to help achieve this.