Well, you're defining the racing "class", so you can make some choices that'll influence how hot it'll get!
If it's going really fast, you may find that you get decent (or even better) cooling by cowling things in pretty heavily -- there's been some pretty specific features of cooling air theory that's been proven true in full scale flight for years, and which can't work differently in model airplane usage. The guiding three are:
- Slow moving, high pressure air cools better than fast moving, low pressure air
- You can slow air down, and increase it's pressure, with a "diffuser"
- Air that doesn't touch a hot surface doesn't cool for squat!
What this adds up to is to tightly cowl your hot parts, with a small, forward facing hole that lets the incoming air 'grow' gracefully (this is the diffuser, that's turning that fast outside air into slow inside air), make sure that all the air that comes in gets directed through the motor and by the battery (or else it's wasted effort), and to pay attention to the air path on the
inside of the cowl as on the
outside.
I'd just build the airplane any old way you like, paying attention to the fact that LiPo batteries really don't like to be discharged too fast. Putting in a "fuel tank" that keeps you in the air for three minutes is probably about the maximum you can go before you start really chewing through batteries.
If you want to get serious about electric racing, I'd suggest that you write up a set of rules, keeping them as simple as possible: I'd start with all pertinent safety rules for racing, a wingspan limit, and a weight limit on the power system (battery, motor, esc.) or just on the battery. Then stand back and see if anyone comes and races with you. As folks find ways to trade money for performance, or safety for performance, or complexity for performance, think about refining the rules to keep the event affordable and accessible, while still making it a good contest.
Maybe you want a maximum weight limit on the battery, and a sponsor-provided fuse of published current value (an automotive blade type would be cheap, and easy to replace). Leave it to the contestant to design his electrical system however he wants to, knowing that if he pushes the current too much he'll be out of the race. This will let you choose a battery weight/fuse combination that won't have people running their $60 battery packs hard enough to burn them out in ten flights, while still leaving you with a system that's humanly possible to administer.