"future-proofing" a larger fridge custom carpentry space is stupid, i'll say it again. this is akin to doing custom bed frame as king size, when you have a queen size mattress, just so that you can possibly in the future upgrade to a king size mattress. it is not just about the large gaps at the sides of the fridge if you do this, you also sacrifice adjacent cabinet dimensions when you do this. kitchens nowadays are already very space constraint, losing even 20cm of additional storage and countertop space NOW just so that you may possibly upgrade to a larger fridge in the FUTURE is a foolish decision.