Hello guys... I have a mustang PST with a OS 46FX and I really like it, I just realized I like warbirds,

I want to build either a hellcat or thunderbolt 60 size... I was just wondering about engines... I'll get definetely an OS 61,

I wanted to know if I can use any OS 61 or it has to be a FX???? I see many kinds of 61, at the club were I go to fly, there are some OS 61 on sale but they are not FX, they other letters......

what do you recommend guys??? or if I am getting a warbird it does not really matter what OS 61????


Thanks.