Update: loving the preFL seats still. No complaints from the passenger seat either

I installed a Polk MM840 into the rear of the wag at last.
Its probably a better choice to use a shallower Kicker 8" or Polk DB840 (?) for a wagon...

I had to make a 1/2" thick cardboard spacer meaning the grille wouldnt fit even with the plastic frame cut out.

Supplied foam ring dremeled out to become a front spacer, if required.

Extra long self tappers required to clear the cardboard spacer.
I used a 9V battery to check the polarity of the wiring was the same as stock.
I'll work out the grille mod later but in the meantime: WOW!
This is one of those "wish I'd done this way before" mods for sure.
Its really opened up the sound of the stock system (plus Resomatted doors and tailgate) and its like I can hear a whole octave lower as well.
The bass is deeper and more defined. I'm contemplating sourcing another MM840 and a 400W sub amp to drive them.
