The whole Poland do.

Wilga is quite powerful and can handle even three gliders at once, but - as pilots call it - it's a 'flying drag coefficient' and consumes a lot of fuel.
For comparision - there's a single plane 'Gniady' with wings and body from Koliber and Wilga's engine, constructed especially for towing - and makes up to 5-6m/s of lift with glider.