hi,
The YS is what CPLR designed it around, if youve got the right fuel it will be ballistic to fly
The OS 70. Id day no, dont know why, just i wouldnet want it
I really dont know anything else about the OS 70 special.
Outher options are the Saito 72, ive heard these are extremly good. OR i have a West Eurotech 50T! (bastically as modified Webra) I rekon these are the YSs of two strokes. I can turn a 13x4w at 13,000rpm on 10% nitro. A YS will do these revs but it needs 20%+ nitr
http://www.westonuk.co.uk/west