The dle20 I have swings a 18x6. But I think what everyone refers is that the midrange rpm is lower than the 120ax, hence the thrust in the hover.

Couple of years ago I and a friend imported a couple of cartons of klotz 100. It was not available locally and we both had reliability issues with plain castor. Premix fuel was also not available then (its available now- Rapicon). He used up his when he put his 120 on the GW Sbach 20cc (Same airplane as Kerwin's, just newer). After he crashed his airplane from a deadstick out of hover, he moved to 30cc. I, on the other hand developed back problems and was out of the hobby for a year. Now I still have 4 or so bottles of klotz and I can always get more if I need. So no harm in going for the 120 if its reliable enough.

Ok. What I am going to do is, decide on the engine as I go along. Then if I have reliability or CG problems, I will retrofit the dle30 if it comes to that

Ameyam