I put big tip plates on a pattern model in the early 1970's. The results were zero because the airplane crashed on the first flight due to radio failure. Oh well ........

Remember when using tip plates, even those I had the photo of, that the lift isn't going to be a great amount. You can calculate the lift based on the total areas - just assume it's a small wing of the same area as the two plates added together. Look at the typical 30% scale aerobat doing a low knife edge pass. It will have an angle of sideslip of around 40 degrees. That flow angle over the fuselage side is giving the lift. The fuselage isn't nearly as efficient as a winglet planform but it can give you a guess as to what to expect from the winglets.

The indoor flat foamy airplanes usually have very deep fuselages and large (very large) winglets and in the case of biplanes upper and lower wing supports. They fly almost as well on the side as upright and are a delight to watch in action.

Our large models of the CAP, etc., simply haven't gotten the big sizes of winglets to be super effective. You might try the two winglets per panel approach and vary the size of each but think about going big. The airloads will be fairly high so make the mounting setup fairly strong. It might look strange at first but if the results pay off then it would look great!

Good flying with them,

Ben