Hi,

I also have a ZEN 90, pulled by a YS110S (new model). I did not have the original WM soft mount so I thought I would use the MK YS110 mount and purchased one, new!
It took 6 flights for the 110S to break the rubber thingies (one rubber mount broke, another one was severely cracked nearing failure).
I needed to get back to practicing QUICKLY so I simply hard mounted the engine and flew almost 80 flights with setup, no problems at all.
There is some vibration, however a "proper' solution would be to use a HYDE mount + nose ring - not easy to implement on a KIT/ARF utilizing the original Fiberglass cowling (although T. Newman did do just that, and successfully - see Focus Sport build thread).

Good Luck,

Danny