Yes, when I went last year the guy who got our tickets was told it has to be a strict mix 50/50 male and female.

However, we had a spare place so there were only 2 blokes and me, and they didnt say a word about it.
As you go through the security entrance to the airfield they look at everyone in the car, I think providing you have at least 1 female with you then you are ok.

If you need a spare female, give me a shout