Hmm, I might be thinking of the old server, or of someone else's hole. Something has a big long ladder all the way up, and a section where the whole wall is covered by ladders.
It can be 2x anything if you have all the pistons on the bottom/top (or anything x2 if you have them on the sides). I guess you could potentially go bigger if you have pistons pulling pistons pulling pistons but the wiring would be prohibitive (and impossible to hide) to say the least.
I'd like to go bigger, but I don't feel like having to do any calculus or needing 3 acres to do it. So I suppose I will take the lazy/easy way and do 2x3 or 4 and just be happy with it.