No pilot, no instrument panel. Basic airplane requirements for pattern are:

11 LB limit.
Max 2 meter wingspan / fuse length.
Sportsman cannot fly retracts or must fly with gear down.
No scale requirement necessary. Most pattern planes are not scale.

Most contests that I've been to would relax the above rules to a degree if you showed up with a plane that was slightly heavy or large. I've only been to about 8 contests, but I've never seen a scale or measuring tape at one of them. Just don't show up with a 44%! Fly it to have fun.. It's a blast!

For full details and rules, go to modelaircraft.org and check out the RC Aerobatics competition regulations. Good read that has all rules / sequences, manuver descriptions, etc. Hope this helps, Chuck