On the subject of shaping the cabinets to fit the bus:- in boatbuilding, where the inside of the hull is a different shape at every point, the builders don't even try to get a perfect fit when bonding cabinets and bulkheads etc to the hull. The bonding is done with epoxy fillets, which bridge any gaps, are very quick to create, and are frequently stronger than the thing being glued.
It's possible a similar technique could be used when attaching cabinets into a bus, perhaps with Sikaflex fillets. The immensely heavy windows in my bus are held in by nothing other than Sikaflex, so I expect it could be used to attach cabinets to the wall with no concern. I doubt whether a Sikaflex fillet could be nearly as big as an epoxy fillet though, so the basic fit of the two parts would need to be closer before the fillet was run into the gap.
Jeremy
(PS. I've just Googled 'Sikaflex fillets' and come across various references to them being used in aircraft construction)
