I too am looking into solutions for mounting my amps on my rear deck. The trunk mech gets in the way, so I am planning on taking my 3/4 mdf mounting board and either suspending it to clear or more likely cut a notch so the bars pass unhindered. Don't want to block the trunk light either.
Here is one post I found with some amps mounted to the rear deck. In the research / parts acquisition phase of this type of build right now.