Has anyone installed the under bonnet battery tray?

[grumpyshouse]

Because I am only wanting minimal solar back up to keep the fridge and heater going overnight I only require a 105ah battery, and I think I’ll manage with AGM or even LA battery which means it will happily live under the bonnet.
Looking at the parts diagrams I cannot work out which bits I need to add or remove or if I just rig up an aftermarket tray.
Can anyone enlighten me?
cheers