You could try making a Kitchen rudder, details are on this forum somewhere. It will allow you to have reverse, forward, some speed control and steering.
When you first see it you might think it's difficult to make but it's not really, after all, nothing ventured etc.
I made one years ago for a Mamod powered tramp steamer, and it was great.
If you want to keep it simple to start with make the model as standard to start with and experiment later, but build with the later modification in mind and leave space for the rudder and servos.
I hope that's food for thought.
Regards, Chas.
