Hey Adam
Yes you can mix them but youll get an average of the 2 fuels in direct proportion of the amounts you mix , IE if you mix them 50/50 then yes you will get 22.5 % if you have more of one than the other ie 75% 25 and 25 % 20 you will get 23.75 approx ...
Be sure to tune from the LSN first ok , levae the HSN flush
Cheers MM