Contemplating buying one of these little monsters; I took a look at this one yesterday.

I knew enough to look for this - mushrooming looks very pronounced, particularly on the passenger side. It appears that a reinforcing plate can be purchased, but not sure if these are too far gone? Any opinions?

 

IMO, they don’t look too far gone but there’s a lot a picture can hide. Most use a block of wood and a mini sledge to get them back into shape.

For external reinforcement I went with the plates from VIP. I feel VIP’s attention to detail really shows in the design of the plates. They are thicker than many of the external plates, don’t have recessed mounting holes, and the machined areas for the ribs on the strut towers are contoured with a nice arch instead of a machined groove with right angles which can have stress issues in the corners. If you can find the NLA strut bar they offered as an option, I would get that too. It was a straight bar which is also better than most other bars that have a slight arch in them.

Pairing the VIP plates with a set of under tower plates should eliminate all chances of mushrooming in the future.

Below you can see the custom machined T-nuts they provide so the mounting holes don’t have to be recessed, and how well they fit around the tower ribs.




Here’s a pic with the optional strut bar.




My hood pad was still very firm when it was all installed so I had to wet the pad several times with hot water to get it to comform around the strut bar. This probably isn’t necessary when using the plates alone or if the pad is worn.

 

+1 The strut plate nuts torque to 25#. Also, replace the plastic coolant expansion tank with a metal one.
https://www.waymotorworks.com/forge-...-tank-r53.html

 

Great to finally see some of your Mini @RB-MINI !
Boy that engine bay looks super clean and nicely appointed with the reinforcement set-up

In addition to the OP's concerns:
+1
It doesn't appear that your strut tower housings are too far out of norm.
As mentioned - simply pound them flat again with a bock of wood, and mount a good pair of reinforcement plates. I would also recommend changing out your top strut mount/bearings at the same time. They are most likely old, squashed, worn and bent.
Installed on my R53: In addition to my (M7) top reinforcement plates, I've also installed Craven Speed under tower plates as well. Great combo. Had done this about 3years ago = not a chance at mushrooming and (IMO) helps to preserve the life of your top mount bearings as well.
You"ll definitely feel the difference in handling afterwards.