I can't wait until they're re-implemented.
I normally stick to under 7x7 - close quarters and cramped tunnels feels more dwarfy to me - but there've been times I've gone oversized. I'd love to load up some of my older forts and see what fun results...
Hmmm... which suggests a couple of possible future improvements.
How about a random time delay on oversized sections? The bigger the amount over size, the quicker the collapse? Then you may not realise you've made an Oops until a season or three afterwards...
Or, to fix the potential "hole in the ground at z=0 because X z-levels have collapsed" problem, how about introducing a new rock "type" of rubble? Which takes up 10% more space than a standard wall tile?
Maybe something like this: a 7x7 section collapses, so a 7x7 section of the level above moves down, right? Let's say that 90% of those tiles become rubble with 10% staying as solid rock. That means that of the 49 tiles falling down, some 44 (rounded up) become rubble, taking up an extra 4 (4.4 rounded down) tile space. That means that there's no room on the collapsed level for 4 of these "rubble" tiles, so they stay in the ceiling level, preventing the next z-level above from collapsing.
Let's say that you have a level entirely made of rubble. That's not as stable as solid tiles, so then the limit should be reduced from 7x7 to, say 3x3. So, when digging out underneath a collapsed area (ie. it has a rubble ceiling) you'd
need to use supports to prevent further disaster.
Perhaps I should move this to the suggestions forum?
Nar... I doubt it'd be implemented. So I'll just have another Bourbon instead and see what other fun items I can come up with...