Don’t glue the mount in place yet!
Here’s what the engine mount looked like when trying to slide the mount in with the tape wrap. I use black electrical tape. Believe me, this wouldn’t work with a wrap of masking tape either. The tube sizes are just too close.
I carefully removed the tape and still pulled off some of the yellow outer layer!
As mentioned earlier, these yellow tubes are thin with a rough outside yellow layer. I wanted to smooth and strengthen the tube.
A drop of the cheap Dollar Store CA was set on the back of scrap sandpaper. A cotton Q-tip was dipped into the CA and “painted” on the back ½" of the engine mount tube.
I also put a line of CA on the around inside back end of the yellow tube.
After drying, it was sanded down with 400 grit. It’s now much smoother and stronger. I only put a coat of CA on the last ½" of the yellow tube that will be exposed out the back of the model. This way, white glue will still permeate and stick to the paper inside the 20mm tube.