It's very common in RC trainers and ARF models. I've used them plenty there. I don't think I've ever done it in a CL plane,  mostly because I've never had an ARF or something that would come with them. In RC, they worked just fine for me.

Well, the engine is mounted, waiting for first flight.  Some comments.

The flexibility of this system looks interesting.  There is enough freedom that experiments with thrust angles appear possible.

The hold-down bars do create issues with clearance around the NVA.  I was concerned that my Super Tigre NVA's tension nut would not be adjustable via wrench.  While that is actually AOK, the short NV I like will not rotate, as it runs interference with the bar.  I'll install a long NV and accept that it may get wiped out with an inverted landing or rough handling when starting or in the hangar.

Peter

John,

Those pins should work great for keeping the motor in exactly one place, speeding alignment at maintenance time.

I thought about the pins, too.  However, based on both theory and testing by others, the mount seemed adequate as-is for my purposes.  Others pointed out that many ARFs use similar "clamp only" designs.  Plus, I'm looking forward to testing the effect of rotating the engine for up/down thrust as part of my ongoing efforts at tuning and trimming.

No real problems with handling the engine on test flights last night, except that I ended up using a longer NV, as the short one hit the mount's clamp bar.

Peter