Just my opinion but the .55 is way overpowered. You will have to put a huge amount of down thrust or be jockeying the elevator for every power change. IMO any glow engine over a high performance .40 is just to much. I run a low performance .40 an old K&B .40 and it is fine except for really hot days, even then it is OK except for the initial climb out over a hot runway. I had a TT .46 in it and I thought it was too much.