RE: Saito 125 Fuel Mix
As BLW Said. The recommendation is not to use fuel that is entirely castor. I doesn't say to not use it at all.
I run 15% nitro in all my Saitos and they are all happy with that. I use 3% Castor and 17% Coolpower (20% total oil) and have never experienced a corrossion problem to date. (I'm also a little slack when it comes to using after run oil).
My sons accidentally filled my normal flight box fuel container with FAI fuel (0% Nitro and 20% Castor) a couple of years ago and all of my Saitos (including the 1.25 we had at the time) ran happily on it - yes we did have a tuning problem and the transitions weren't great but they ran happily all day nevertheless.