Lee, I haven't personally seen a boat such as yours but I'll take a stab at some answers for you.

1. I doubt if enlarging the sail or mast would be a good idea. It would probably only add to your difficulties.
2. Increasing the ballast is probably not a good idea either. This would add weight and more drag for the boat. Both of which are bad things.
3. If your friend gets the same boat, he will have to have his radio on a DIFFERENT FREQUENCY from yours or neither one of you will be able to control your boats if you sail at the same time.

You say it's hard to operate using just the sail......I assume the boat has TWO control channels, one for sail and one for the rudder???
You should be using them both together. What does the boat use for rudder? Does it have a seperate rudder or just use the outboard motor for steering?

Anyway, I'm glad everyone is having a good time. Sailing is very addictive and I suspect soon you will be wanting a pure sailboat. Check out the Victoria made my Thunder Tiger.

Also there are many good sites on the internet with information about HOW TO SAIL. You'll get a lot of good information about the technical aspects of the sport there.

Welcome to the world of sailboats!!! jim