Under the hood seems very enticing and adds to the utility of the rigs for sure. I almost did this recently but decided against the under-hood install.
After reading up on compressors and duty cycle and how to extend the life of the unit, it seemed that heat and dust and moisture were things you wanted to reduce as much as possible.
Those factors seemed to increase with an under hood set up.
Now if you really wheel alot a d would use it frequently, maybe it's worth the trade off for the benefits on trail with the air tank, air tools, etc.