Bidwin,

I replaced an OS 120 FS with a DLE 20. OS 120 w/muffler weights about 32 oz. DLE 20 weights 29 oz with muffler and ignition modual. But it will need a battery so weight comes out about the same. The DLE 20 is slightly longer front to back than the OS so you should measure for that or expect to modify the firewall area. You have more flexability re the cg because you can put the battery were needed for cg. On one of my gassers I had to put both batteries under the cowling to get cg. On another I put the battery way back in the tail under the rear stablizers to balance. The DLE turns the same prop 300 rpm more static that the 120. Also the DLE is shorter top to bottom except for the spark plug boot. I've put DLE 20s on airplanes from so called 60 size to 120 size. I'll admit the 60 size is somewhat over powered, but the 15-17 cc gasser have about half the power of the DLE 20 and are only an ounce or two lighter. I have a couple of RCGF 20cc gassers. They are heavier at about 38 oz. Ok if you need the weight. On flys a 90 size plane just fine. The other is on a 120 size plane and is "just enough". The DLE turns the same prop about 500 rpm more than the RCFG.