I don't believe its practical to scale a model directly in regard to power and weight. For example a 1/4 scale model directly done on power would take your 100hp and knock it down to 25 hp. I can't see how an engine that size in the model size your talking would even work. Your 1200 lbs at 1/4 scale woud be 400 lbs. The RC limit I believe ia 50lbs with special waivers, etc. Scaling to model size from 3-views is more about dimensions than power and weight as they are not linear to size. I dont think it matters regarding weight and horsepower. If you build a 1/4 scale model of the real thing and it flies then your good. just figure the HP needed for the real plane irrespective of what the model is using. Just my opinion and probably should be taken lightly since I've never built anything full scale.

Here is a cool site... look at the WW1 replcas most 80% or scale. Look at weight, HP, etc then find the RC kit (1/4 scale, etc) and compare mathematically the scaling, weight, and HP requirements of each.

http://www.airdromeairplanes.com/
Mike