I have some experience running 30-40cc on 2 meter planes. But not the 20 cc on 1.7 meter. I suggest that you pipe the engine with the ESComposites 26G pipe. Should be able to turn about an 18-6 to 8 at useful rpm.
the small gassies put out just so so power on mufflers but seem to really come alive on pipe. Try it....
thanks a lot MTK! Would it be a better choice to use a NIB Rossi R 90 FI RC with a long tuned pipe? I have this engine lying around on my workbench for a long time. What do you recommend? Use the DLE or the Rossi?