ORIGINAL: Truckracer
I wouldn't tolerate that kind of flex and don't especially care for any of the molded mounts. Hanger 9 makes a decent universal aluminum mount at a fairly good price. These have worked well for me in the past and are the same as supplied in many of their ARFs.
Yes, a flexible mount can be very hard on your muffler and airframe.
Is this the mount that you're talking about?
http://www.horizonhobby.com/products...61-2-2-HAN2033
I was considering changing to this when I first noticed the movement on my current mount. I just wasn't sure about the slotted mounting style? Has an engine ever moved on you?
Z