ABC R/C fuel into 29% all castor

I'm running low on all castor fuel and am going to have to mix some. For a baseline lets say I'm starting with a gallon of 10% nitro and 22% oil which is 50/50 castor to synthetic. Do I ignore the synthetic completely and add the castor to arrive 29% or do I partially discount the synthetic and add less castor?

I've been told on other threads to make the fuel up to 29% total oil - castor and synthetic.

I agree, although all castor probably would be better for your Fox 25 (I think), 29%castor +the ~10% synthetic would be too much oil. I happily run my Foxes on 25% castor (Sig Fuel), and they seem happy.

Yes others have said that they run on as low as 22% oil - but they are experienced engine people who know how not to accidentally get the odd 'lean' run that could cripple Foxes or McCoy's if there's not enough oil in the fuel.

I've seen some stories on boards of these motors being run on low oil fuels - they're fine until that one 'lean' run that can ruin them.