Front trans mount: Originally modified because of the SLP headers hanging down and interfering with the strut part of the mount. The strut does act as a limiter to a degree. This was a first version/idea that I had after shredding a new one that had the strut missing. Grade 8/10 bolt with hockey pucks as support when at rest. I never noticed vibration at any speed/TC lock up etc.
FWIW, I've watched the antics of someone that chose to put a weak bolt though theirs etc etc and even recent revised versions were tearing apart. The most current version looks a lot like our stock mount minus the strut, then adding a bolt through the rubber.
Lots of power has been held by the mount I made. Mike would know much better than I about angles etc and which place the bolt would do best in (through rubber or in place of strut like my design) as he applies this type of engineering and I'm more of a farmer. All in all though you could see my subframe flexing with the motor movement and the mount never showed any symptoms of breaking.
Torque Axis mount: A bunch of Riviera guys were doing these and other mounts in urethane. After doing a little research and finding many of us with a TA mount see constant failures from increased power, this was a project to try out.
Picked up some urethane, and a toilet bowl wax ring.
The idea is to clear out the mount and fill it up with the metal sleeve for the bolt in place. I used cardboard and the wax to seal up one end of the mount. Then fill with urethane. (note: do this in a disposable tray like cardboard or something)
So then we have to rig up a method to test. Watch the car/mirror next to the Bonneville. With the brakes on as much as a leg can hold them, the car is pulling itself forward. The squeaking sound is the tires dragging/breaking free on the concrete. I got on the car much harder with the urethane mount, and the marks on the cardboard are at 1" increments.
Before urethane (new stock mount)
The urethane seperated from the metal of the mount and could use some form of bonding goop (like they use to adhere the rubber to the metal on our front trans mount).
Dan.. I've mentioned the front mount to you before. If someone sends me a good front trans mount, I'll send you the one I was unable to break. All I need is a mount to put in it'* place. And if you'd like the urethane one as well (its just sitting on the shelf) for testing etc. I'll toss it in the box at the same time. Both for the cost of shipping and getting a trans mount here for me to put in the car. My Bonneville is demodded and no longer needs either mount. Overall, I'd say a good front trans mount was noticable and worthy for putting power to the ground and the TA mount wasn't as noticable. I was trying to keep from tearing the TA up though. Mine would constantly look like yours does at the moment.
Another idea I had was getting some material and routing the shape between the large part of the TA mount and the engine side of the mount into it. Then putting that as a spacer between them to limit movement. That way the open space where the metal sleeve is located is filled. This was one thing I didn't get around to doing/trying out. The material has to be soft enough to not transfer vibration (would cause KR) and be sturdy/strong enough to take the power. Ideally this would almost be a redesign of the body side mount that includes the shape of the engine side. Could probably be done with both mounts assembled, then find some way to build a structure around where the urethane needs to be. Put a release agent on the engine side of the mount, fill and once hardened, the engine side mount could slide off. Then it would have the correct shape and be solid with the rest of the body side of the mount.