I had my very first tows last season with my Multiplex ASH26 ( 4m), behind a Telemaster. I don't know exactly what kind of engine the telemaster had, all I know is that is was a OS 4-stroke.
Anyway, it towed the 12 lb ASH with ease.

To the tow itself : We launched with approx 1/4 inch flaps deployed on the ASH, and after that it was only a matter of keeping the wings level, and letting the tug do its work.