I'm with AeroDave on this one,just use up spoilerons. How much is up to you. I had one plane with split flaps/ailerons and never found much use for crow(this is not a sail plane with small surfaces) I used spoilerons(full span) for windy days when the Do tended to keep on flying or jump 5-10 feet straight up in a gust. Also, a tail heavy plane will "sink" more predictably with spoilerons. I used to be able to head straight down,low throttle until it almost hit the ground and then pull up to a slow landing without any speed build up with spoilerons,I have seen another guy do it with crow but I dont know how he worked it all out,it didnt work well for me. If you have a Futaba 9C,you can do the craziest mixing that is available.(or 8U for that matter). One thing I had to do with that mix was link the spoilerons to elevator. I had them set up to go up with Switch C,but if I pulled up elevator,they would come down in a linear mode with the elevator motion. I did this because on the final approach the plane would drop too much even with up elevator(wing is always loosing lift)and would hit pretty hard. When I mixed in the elevator, when I flared to land,spoilerons dropped and wing regained lift and the plane landed normally. I also used to open up another set of P-mixes and add in throttle-Spoilerons,set offset to about 1/3-1/2 throttle,then if I had to throttle up suddenly(bail out of something) the spoilerons would also drop to neutral in that situation too. I dont think the Giant Do will allow the latter,it would require 3 more P-mixes I think,not sure if you would have enough. Any way the spoilerons alone are effective as air-brakes IMO.