Just a suggestion but how about two four minute qualifying rounds and one five minute final and starting at 6.30? TQ qualifying with top qualifier gaining one extra point and then points for wherever you finish in the final.
The problem with two finals that both count together is it doesn't allow for mechanical failure or someone being taken out by a slower driver and can often mean that the fastest man on the night can TQ, win one final by several laps and then have someone take him out on the first bend and break his car. This means that he gets the extra point for TQ and one win but because he doesn't score in the second final he gets beaten by someone that is far slower. Just my opinion, but it seems a bit unfair
By having two qualifyers that are slightly longer than you have now it means that you get a more even spread and the qualifying is more enjoyable. Also you probably need to reduce the time in between calling the cars off at the start to one second intervals, as in most heats the first car was already coming down the straight before the last car was called off. In a couple of cases the first car had already overtaken the last car off before it had actually left the line
I think the extra hour would work a treat, just not sure which end of the night it would be best put. If it's at the start of the night some people won't be able to make it because of work, if it's at the end of the night then some people will undoubtedly declare that it's too late for the smaller children. I doubt whether everyone will be happy whichever way you go but you can't please them all
Sorry if i'm out of line to comment as i'm not a member yet (I will join in a couple of weeks) but hopefully all comments are helpful.