I've done this and the portability and small foot print is great, as I don't have a dedicated brew area. I guess the plastic on the box I have is extremely thin. I used the same screws that came with the pump.
I did have problems with heat that were mitigated by propping open the lid with a short piece of CPVC scrap I had. I initially ran my pump for the entire mash recircing. Now I only run it when applying heat to the kettle.
I brew in a single vessel and no sparge. Now I only run it while applying heat and then for 10 minutes during mash out. I really haven't had problems, but I keep the lid propped open regardless. So maybe a total of 20 minutes for the mash and maybe 30 min while whirl pooling.
I mounted my pump on the back side of the tool box, so the lid also works as a guard against splashing even when propped open.
The box I got has a tray in the top which I keep my brewing salts and minerals and a few tools I often need.