A while back I read some threads about folks that replaced the 2nd cats with test pipes having trouble cooking the inner CV Joints. (Note the major heat shields on the factory mid cats). I have the Top Speed test pipes installed and so I was concerned. I tried doing a header/exhaust wrap but that was really tough with the pipes already installed in the car. I then found this product called "Heatshield Armor" which is designed to reduce radiated heat from exhaust components. I bought some and installed it on my car, and it was pretty easy to do in place and looks like this when installed.
You can read more about this product here:
https://www.heatshieldproducts.com/automotive/exhaust-heat-shield-insulation/heatshield-armor
This video shows how to trim the heatshield armor and fold the edges back, and also shows how to install the stainless zip ties. It is on a bigger muffler component but this is the best video of the ones I found.
https://youtu.be/aRRDEK9wwjs
I got it all from Amazon but there are plenty of places you could get it from.
These are the stainless ties I got:
https://www.amazon.com/gp/product/B00CTKBTH2/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
This is the Heatshield armor I got (6" x 5')
https://www.amazon.com/gp/product/B004SRH2KC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
Prices seem to change a lot on Amazon so you might be able to find a better deal and/or more convenient size somewhere else.
I don't have any hard data to back this up, but the heatshield armor is supposed to block 70% of radiated heat, so I figure it has got to be keeping those inner CV Joints cooler.