ircphoenix
En-Route
I think you have this backwards....
Tach runs slower than Hobbs. So if Hobbs runs 20% faster than the Tach, you can charge "less" for the Hobbs than you'd be able to charge for the equivalent tach time.
So if the Hobbs rate is 100 an hour... for 1 hobbs hour, a tach hour would be .8 ish. So to get your 100 bucks for the same tach time, you'd have to charge $125/hr tach time.
If he feels better because he's paying a higher rate for a slower clock instead of a lower rate for a faster clock, that's his business, I guess... but I don't know many operations that aren't going to know that the tach runs slower, and adjust their prices accordingly.