[roger1]

Glad you asked this Muslcah.
Base gets reduced at 1:1. 4 gallons sprayable. It's a lot for a convertible, I know. But I like having left over color. Saves color matching headaches if anything happens down the road. I intend to make my car a keeper.
I probably should be able to do this car with 1 gallon (2 gallons sprayable). But I'd feel better having a gallon plus 1 quart on hand to start with. Then I think about pricing and the potential of something happening to the car and needing more and choose the extra gallon instead of the quart.
I was happy to have the extra paint on hand with my last project when my El Camino got caught in an unexpected hail storm 2 years ago. I didn't have to repaint the entire car but a pretty good percentage of it.

SPI Universal Clear is also a 1:1 mix. I never mind having extra of their clear. I always end up needing that for things and never buy just a quart. But, it's always better not to buy the hardener until you need it.