Manhole; How big is better?

Just about to start the first stage of the reno, my cousin is a registered builder and will be giving us a hand for a while until he gets his Driving License back, but he doesn't want to give advice ( I fully understand this ) except on actual building matters.
We always keep the boxes that our stuff comes in and I want to put them up in the roof space.

I want my cuz to frame up the new manhole ASAP so we can start moving stuff, corridor is the obvious place but the old manhole is where the new linen cupboard is going.
Question is how big can the hole be before it starts to get unwieldy.


Read the full thread at RenovateForum.com...