Hello Freinds

I have a quick question about mounting a panel in my garage. I installed a "220 amp pass-through panel" under my meter outside. It feeds a 100 amp panel inside via the pas-through lugs and will be servicing another 100 amp panel in the garage through a 100 amp breaker installed inside this panel outside.

The question I have is when I bring the feed inside the garage it will be at foot level and then come up. The idea I have is to mount the panel upside down so that the wire can go directly into the panel. All circuit wiring will then come out of the bottom, go up into the attic and then feed wherever I want throughout the garage. I figure this was the cleanest route to get to all the walls, around doors etc and then bring wirind down to appropriate level for an "in-wall" mounting of all boxes. Is this kosher? Can the box be mounted upside down? I may run conduit out of panel and into attic...any ideas on that? Thank you for your input!

Barry