Not as scary as the movement on the brake servo, mind you that is a lot more obvious than the slave cylinder.
My car was built in 1998 & has done more than 125,000 miles, although I’ve been conscious of the problem, such as it is, since I started to look at the MG horror channel on YouTube, you would think the roads would be lined with our cars suffering from failed mounts by some of the fuss. I’ve never been moved to buy or make one, although I can understand why folk would be inclined to do so.
Nor have I seen any reports of improvements by fitting one.
If you go for it please report back with your before & after impressions.
M