RE: Kyosho Spitfire 90
I was using a MA s2 props,16x8 with the saito 125. It put more load on the engine creating a better sound compared to the 16x6 I was using, slightly better speed.
But you are using a 120, so you will probably be be using 15x8, 16x6 too,
I do recomend those MA s2 props. Horizon uk do them. They are less prone to breaking than the apc but still very efficent.
As for the retracts I used stock. Just go easy on them
Later, I drilled out the retracts and used slightly larger piano wire, straight leg too.
good forum info on the 90 spit here.
[link]http://www.rcgroups.com/forums/showthread.php?t=953813&highlight=kyosho+90[/link]