ALLOY WHEEL CHOICE HELP

Hi all looking for a bit of advice on wheel choice, I want to upsize to as large a wheel as possible but still retaining a decent amount of tyre for a comfortable ride, I got a set of 16/205/60 et35 on atm but hoping to go up to an 18" wheel if possible, can anyone help with what's the biggest I can go with at least a 50 tyre on there & what the best offset to go with is, I actually want the larger wheel for a bit more clearance so basically as big as I can go will be good, any thoughts???

You'll be wanting to look at this thread:

https://hiace-super-custom.forumotion.com/t2980-alloy-wheel-sizes-on-a-super-custom

Thanks for this :-)