Hi,
For 90 size I think this setup is great :
- Engine : YS 140
- Prop. : APC 16 x 6 or 16x8
- Servos : JR 559 MG or Hitec 5645 MG
- Batt. : Futaba 1500/6V or Duralite 2400
- Fuel : CoolPower 30% heli
I used this setup with my ShowTime 4D 90 and Funtana 100X, it was awesome.