I don't think you're being thick, great idea.
I've come up with a sketch of the car with adopted logo placements and approximate size - each location has a different price (12 months placement).
I've only got one interested party though
Each one is a percentage of the overall expected income. E.G large massive symmetrical rear quarter and doors = 35%. Small door shopping lists = 5% each. Until it adds up to 100% of what I think acceptably covering the car enough not to make it look sticker bombed.
I've summarised the costs (taking some out for what I expect to pay personally to get the general enjoyment etc! As I'm not just in it for the coins) but the most expensive bits are estimated on the number of events and how long they'd last.
-Tyres
-Event Fees
-Discs & Pads
-Engine is shaggered at some point fee
The rest I'll pay, Fuel, transportation, general niggles and upgrades/improvements etc. But obviously you'd compile your own list.
Calculate the approx. cost per usage on a rough event and apply the percentages.
My last attempt:
In 12 months:
3 Track days
2 Sprint events
Approx costs:
Tyres = £600
Event Fees = £900
Brakes = £300
Disaster recovery = £250
Total = £2,250
Biggest sponsor pays: 35% for 12 months = £787.50.
Door shopping list sponsor pays = £112.50
I've even drafted what the sponsor would get... 2 pictures per event, 1 free passenger ride per track day... etc.
I am yet to do any of this mind you. I'm half Spanish and the 'doing' side of things is definitely the half that's from the continent.
P.S They pay the bill for the vinyls + fitting.