I think:
1) Solder all wires properly
2) Screw sub-box to seat & boot floor using those "L" brackets.
3) No MDF parcel trays. If you do use them, make sure they are screwed down, and not liftable.
4) Amps to be screwed to MDF planks, and MDF planks to be screwed to the rear of seats/floor of boot. Floor of boot maybe better.
5) All screw-holes of speakers and amps to be used to screw them down. Eg: Some installers may use only 4 holes out of six in speakers, etc.
6) Maybe using a foam backing under the amps before screwing them to planks would be good? Gurus?
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