I will give you the same advice i give my kids.What is the best way to start preparing for this event now/over the summer?
Write down everything you learned this year. Write down any random thought that pertains to helicopters. Then think hard about what you want for next year. Make reasonable goals. First in the nation is not reasonable. Top 15 is. or Top 3 in your state. Then think about what you need to do to get there.
Then put it away for 3 months. Don't work on the specific event. Take the time off. Join boy scouts/girl scouts whatever. The biggest risk you will have is if you work on it all summer you will carry any bad habits/design you had this with you to next year. Plus, come Feb you will feel burnt out.
If you have too. If it's in your blood and you can't put it down. Learn everything you can about general astronautics. Find out how props and thrust interact. Read about how the F1D people combine rubber, props and their pitch. How does that differ from penny planes?
Find out how balsa wood is selected. Find out how they cut the ribs for the ultra light wings.
If you want to win. It's not about building the best thingie. It's about understanding the problem better than anyone else and finding the best solution. Next year they will print the manuals and it will have a specific problem to overcome. You want to be that person who knows how to do that.
Because when it comes down to it. The best skilled builder will lose to the best solution.
So my advice to you is. Don't work on helicopters over the summer.