Welcome to the RCU forums, basslakeflyer!

You can find some recommendations for a second plane in these threads:

http://search.rcuniverse.com/search....hwhere=subject

Responding your question: Yes, bigger planes fly better, but it is more due to a wider wing chord and bigger inertia than to a longer wingspan.

Are you sure you have done all you can do with that trainer?
Maybe is the trainer who is bored of the pilot?

I bet you have not learned all you can from that trainer in just two months.

Best luck with your second plane!