My big rear hatch is like a semi when open.
It runs on nylon studs on stainless rails, I have tried rollers and don't like the sudden stops when at the end of travel, they run a bit too freely for me. They tend to shoot forward when you hit something.
As it is heavy to open from inside and would be a problem when it rains, getting the engine room wet, I put a normal size sliding hatch on top of the big one for the best of both worlds. I can stand inside the doors with a poncho completely covering the hatch if cruising in the rain is necessary.
Very happy with it, I will copy it onto my next boat.
It occured to me that this is an ideal way to convert a semi trad to full trad. There are lots of semis that have bad rusting in the rear and too many doors, they sell cheaper than proper trads.
Can't do a pix, far too far away!