I can't comment on the engines, but I will throw in a comment on the glider....

Towing a glider can really be fun, BUT I would strongly recommend that you attach the glider's tow-line to the CG of the Tow Plane - not to the tail.

In full-scale glider flying, the first thing you are taught is to keep the glider down. You see, because the glider is a high-lift aircraft, the tow plane is pulling it faster than it wants to go. Therefore, the glider will rise faster than the tow plane.

Now think about it, you have a glider attached to a string, lifting up on the tail of a tow plane. Unless the glider pilot can keep the glider down, he's going to pull the tow plane's tail UP

Pull the tow plane's tail up, and the tow plane's nose goes DOWN, and once the tow plane has gone into a dive, it will pull the sailplane faster - creating MORE lift (See where this is going?) there's nothing the glider can do but go down with it (Or release - but this usually happens on, or shortly after take off, so there often isn't time).

If you attach the tow rope to the tow plane's CG, as the glider rises, it will just help to lift the tow plane.