As for the trunk rods - they can be removed CAREFULLY and some thing else implemented. Some have used gas shocks like hatchback cars or you could look at coil springs like my SX 2.0 came with.

 

Some amps are more conducive to being mounted upside down. For example MTX amps have their heatsinks mostly on the sides with very little in the top. These amps can be mounted upside down with better thermal results.

 

There is no room for hot air in any amp, whether it is mounted upside down or not. The parts that generate heat are mounted on or near the heatsink, which draws the hot air out of the part and allows it to be dissipated into the environment.

 

Anyone opened up an amp lately? The last few I have peeked at showed all the components with the bottom off. Typically the circuit board is mounted more towards the 'top' of the amp. This would mean that with conventional mounting the parts all hang upside down and, in fact, in this configuration any hot ambient air would be trapped amongst the devices by the board.

Turn the amp upside down though and the hot ambient air would be free to rise off of the board to the back plate.

As DWVW said - some amps cope with upside down mounting better than others.

 

it realy depends on how hot the amp runs .I had an old set of alpine amps mounted upsidedown under the rear deck of my malibu for years, never any problems ..amps back then (89) were built with adequate heat sinks ..I find sme amps nowdays seem to scrimp on the heat sink in the name of small size

I say try it .if the amp thermals out on you then maybe look at a new mounting place