My wife needs a more protective case than the Peak Design provides but I wanted to move to PD vent-mount phone holder. By carefully cutting a matching hole in the back of the rubber outer case I was able to attach the “universal” phone mount to a compatible surface. Note: you keep using that word (universal). I do not think it means what you think it means. This retrofit works great and almost looks like it was designed this way!
I purchased this to use with my Peak Design Evotech Fuel Tank mount with an S20 with Tech21 cover. I was hesitant to use it on the Tech21 cover as it is semi flexible. After mounting to the cover, waiting 48hours (instructions are 24hrs), and going on a few short trips it has held up. Now, I have logged over 2k miles with this attached to my cover on the motorcycle and it is holding strong. I am quite surprised at the 3M tape holding as I have had issues with this tape holding inside vehicles and not exposed like on a motorcycle. No problems to report. I am happy with this mount and will purchase other mounts when I change phones.
I bought this to convert a phone to a dedicated dirt biking computer, haven't had the chance to go for a ride yet but it does feel sturdy and the magnets are pretty strong.
I use it for the motorcycle mount and it works good. To be honest I'm scared in case it detaches from the case, but it doesn't look like it's gonna happen.