I think I will resolve this quickly, but I still want to bring this into issue to make sure my calculation is correct. This is in preparation for tomasbrod/Interstellar#1 .
Mass ratio for Kerolox as listed on wikipedia is 2.58 - 2.77.
The game unit is volumetric, so we need to divide by density.
2261.17 1219.51
Normalizing that to fraction gives:
0.64963 : 0.35037
0.66563 : 0.33437
The F-1 engine burns kerolox at r=2.27, converted to volume and normalized gives:
0.61997 : 0.38003

Neither of which is close to the 0.4564596 lox fraction of CDT. If no more data suggesting otherwise is found, I propose to set the tank volume ratio to approximately 0.65:0.35.

Are there any mod engines using Kerolox currently?

Yeah, RFStockalike defines lots of kerolox engine configurations, I only checked on of them and it is at 0.62305 lox volume fraction.

propellants.xlsx
Because github is now micro$oft, we are forced to attach spreadsheets in m$ format.

RealFuels Stockalike config:
Methane - 43.37 : 56.63
Kerosene - 37.69 : 62.30
Hydrogen - 76.31 : 23.69