POLYLOC MOTOR MOUNTS
How long ago did you buy your last one?
First set bought in March of 2012, I know I got another set in 2014 and bought their brackets with rubber mounts in Jan of 2018.
So somewhere in there they sent me a 3rd set of poly locs.
Timeframes were dictated by availability, whether in stock or not, r&r, heat shields, weather, etc.
I never felt a vibration, never saw the engine move while driving.
I've driven it with a hood scoop and just a hole in the hood. No way heat is a factor.
If I were to design them, I certainly would not allow the two opposing sides to slide past one another vertically - that's exactly the direction the engine is twisting.
I don't doubt they work for some, however I believe they have failed for some who never look or notice.
Whatever the mount, the counter sunk bolt through the mount with a loose fitting lock nut is the way to go.