jrf, do you have any sketches or drawings for the 90/120 twin nacelles? No, but I started with the Super Sportster Twin plans from www.RCMplans.com. Plan #930 I just acquired one this morning and the wing is already built. I would like to make it a twin and have a couple of questions.
Did you extend the center section sheeting out one wing rib? Yes
The wing is built for taildragger landing gear. I think it will be a simple task to cut open the sheeting and install another set of landing gear blocks for trike. I agree. Would it be best to try to cut off the wing tips or just cut the last rib and extend everything with a new rib from this location? I think it would be easiest to cut the spars and trailing edge at the inside of the tip rib, add a rib, extend everything 3 1/2" and then glue the tip back on.
I also like the idea of 2 elevator servos. Did you mount the rudder servo in the tail, also or in the fuselage under the wing? Do you think it would be too much weight to locate 3 servos in the tail? I put the rudder servo over the wing and used pull/pull cables. Weight isn't really the problem, space is.
I would gladly pay you for any drawings you have. Sorry, I don't have any drawings, but if you need any specific details, I might be able to send photos.