I think the team event rather than single car endurance will be a lot easier to put together - teams of 4 means that with 20 takers thats 5 cars on the track at a time, 40 and its a full grid so it doesn't take massive numbers.
I've done a 4 hour and that was a pretty good time length to go for. With a team of 4 its actually pretty busy - you need one driver on, one marshalling, one ready to go on and one in the pits getting ready. No time for naps!
I am however seriously disappointed with Gav, Chris and Budfish - I thought we were in for another storming Bury Metro Oople-fight but you settled it all quickly and in a grown up manner, before I got a chance to get my alter-ego out and start deleting.