I was thinking about using a setup similar to yours. I looked at the OS 120 FS right angle headers at Tower...they show two right angle headers that look identical, but with different part numbers. Also, it appears that you used the short flexible extension...is that correct? Have you considered using a pump on your OS? I've never tried an external pump....not sure how user friendly they are. Did you mount your servos in the tail to make it balance?
ORIGINAL: Don M.
I used a Dubro vibration mount on mine ( pictured above ). It is all the mount you need and the only one I use on on my glow engines. The one I used on the Venus II is a #686 which has a bit smaller footprint than the 688. I turned the tank sideways and dremeled a bit of the former out so I could lower it and mount the engine fully inverted - mine is a non - pumped engine. Looks and works great that way. Treat yourself and use an inside header and a flex pipe so the muffler exists under the plane as in the above pic. I get very little residue on my plane that way.
The 120 FS will give you unlimited vertical and only uses 10 - 12 ozs. of fuel per 10 min. flight.