when I ran with the 205/50 R15 tires, i could fit all 4 in the hatch standing up in a row, with out seat folded down. the rest of my gear I put into a large rubber tote (with lid, ~50L or 12 gallons), that i sat on the back seat.
now with the 225/50R15 tires, they are too wide to all fit in accross the hatch, so I have to fold the seats down, put 2 tires on the seat backs, stand 2 up in the hatch with the tote.
the nice things about the tote is that it is easy to load and unload the car, and store it in the house. all of my race gear is in 1 place, and it usually means i dont forget anything. also, if it rains at the event, anything i want to stay dry can be sealed into the tote
I should also mention i put tire covers/carry bags, made of nylon on each tire when i transport so i dont scuff/scratch the car or dump the dirt all inside my car.
for auto-x: '04 Liquid Grey ZX3
for street: '02 Infrared SVT