I had a gentle lady with a tee-dee .049 power pod. I ran the tee-dee with crank pressure to the tank and a fairly hot fuel. I believe the prop was a 5 1/4 x 4. This was barely sufficient to get the plane in the air. If I had to do it again I'd use a .09
Wow - that must have been a heavy GL. I had a GL years ago with a TD .049 and it was fine. I also flew an Olympic II for years with an engine pylon cut from 1/4" light ply to fit as a "rib" between the two wing halfs with the same TD .049 on it, flew great with enough run-time to get fairly high.