hi - I built the .40 size extra 300 from Great Planes - see pic below

I am pretty happy with it except I cannot get it to flat spin...

I tried, starting from regular spins, both upright and inverted, and what happens is when I decrease the ailerons and start making them opposite to the rotation, the spinning stops. I expected it to flatten and keep spinning... I already read the threads about flat spins but I still can't do it ... Does anybody have the same aircraft and manage to have it flat spin? I need help with the sequence of control inputs, maybe CG location and control throws too...

thanks

I followed the instructions except I replaced most of the sheetings with thinner and lighter balsawood. I can't remember the weight (built it several years ago) but it's pretty light. The engine is a .46fx OS, and with 0% nitro and a 12x6 graupner prop, the thrust is greater than the weight of the aircraft, I get unlimited verticals. I can also get it to make 3/4 of a knife edge loop, which is pretty nice... Only the last part (the downward->horizontal part) fails. It is a very nice airplane, I just need fine tuning to make the most of it.