Recently I searched the forum and found some guidance on the 2010 XFR motor mounts. In particular in my case was the drivers side (LH) engine mount. I have a portable mid lift to get the car off the ground. What first appeared as a HUGE job got easier as I figured it out during the process. I also added an auxiliary cable to help ensure it doesn't happen again. This is how I accomplished mine... feel free to correct or offer a better way. Upfront the mounts are filled with fluid, and most leaks are evident with a purple fluid that stains the mount. The factory mount also has a nylon cord across it..but it does very little to assist the mount.
Onward: I removed the reservoir uptop, dont know if it was neccesary, but when lifting the engine...didnt want to get against it. I removed the bottom pans. Eventually I had to remove the 3 bolts from the steering rack, unplug the electrical connection on the rack, and pulled the lower steering coupler bolt and separated the steering U-joint. It has a flat spot milled in it so that you can reinstall without worrying about aligning spines. I used mechanics wire to secure my steering wheel to center so that no one would turn it. Support the rack with cord or wire as it can put some pressure on the steering hose if left free. Once the rack was pulled down out of the way, I removed the lower engine mount bolt, then used a floor jack and block of wood to lift the engine up far enough to remove the broken bottom part of the mount. There is a place near the front of the engine on the left side that has room to get a block on it. This also gave me enough hand room to get to the top bolt and loosen it so i could remove the top part of the mount. I had to jack the engine some more then I replaced the broken mount .....now for the good stuff. I went to the local hardware, got 2 foot of 3/16 cable and some aluminium swage connectors. These swages can be used with a swage tool or an anvil/vice and a good 3lb hammer.
I made a loop that would fit over the top engine mount bolt with a washer that would not allow the cable to come out around it. I measured the cable down to the engine cradle and allowed about 1.5 inches of slack and completed the lower loop. The cradle/crossmember already has a nice bolt hole in it all the way through, so just get a bolt long enough. Do not affix the cable to the crossmember yet. Tighten the top mount bolt with the cable in place. Lower engine, tighten lower engine mount bolt. Reattached the steering rack and tighten, making sure the cable is ran between the rack and the steering rack attach point (there is an area that is open enough to easily fit the cable) if you did your measurements right, the cable should be ready to bolt to the crossmember/cradle with the bolt using a substantial washer. Replace bottom pans. Note: ensure as you route the cable behind the rack, that it is not near enough to the steering universal joint to make contact with it. Now, this should prevent another broken mount as under load the cable should prevent the over extension of the mount to the point of breakage. Picture of cable makes it look bigger than it is. 3/16 is what I used. Hope this helps someone, as I dont want to break another mount much less do this again. I am told the R/H mount is relatively easy in comparison.

Cable with swage

 

What were the symptoms that lead you to diagnose and repairing said engine mount? You've provided a great solution to a problem for which I have no clue on why you needed to do this.

 

The way I discovered this was after a couple of times of running 20mph-ish and stepping down on the accelerator fully, when i let off at say 60-70mph, I felt a small "bump" in the car. The best test is to put your car in drive, hold the brake and slowly...slowly start pressing on the accelerator. If the mount is bad, the engine will try to lift the L/H side up...like 3 or 4 inches. The mounts are pretty expensive, so if I can keep from buying another I will.
I most likely did this with a heavy load in the car and a hard tacky hard launch or I did have one instance of jerking the car while in "S" mode once, as I was not used to it. Not sure how the mount happened, it may have been that way when I bought the car, as I have only had it a few months, but I don't remember a 'bump", so it was likely me.

 

Okay, this was the symptom that I was looking for. Thank you.