23 % , these days . olde times it was 20 % and burn them up eventually . All C or 3 % syn , to delacquer as you go .

These Lapped Supertigres you get a shiny narrow band around the piston  , just down from the top .

if theyre any good , about 1 mm deep after a few hours use , going to maybe 2 mm .
if it goes half way down the piston try 60 % N or give up , as its ro%#ted .

3:1 fuel for running in , or 30 % initially , then 25 % for a while . Patiance and youd gettem really good .

The 29s ran 8X8 Bartels for T/R , the .35s for combat maybe 9 x 7s  , mine with its small veturie 4 stroked nicely on a 9 x 6 3Bl in a stunter, unmuffled .

I think we used 20% synthetic oil back in the day.  Then the Cleveland guys put me onto Greasy Kid Stuff: modified soybean oil.  15% of that was enough.  Castor should be OK, too.  Don't exceed 30% nitro with the stock bearing. 

The best prop, believe it or not, is a Y&O 8-8.