Due to a miscalculation, I may be forced to mount my amp on the the same plane of my subbox. I see guys all the time mounting on the side of their boxes, will it be a problem if its on the same plane? This will only be temp, gonna design a box that is higher/less deep so I can mount both my amps on the back of my seats.

 

No worries...you be fine. As long as the amp isn't upside down or something like that. Give it enough space to cool and you're good to go.