Mining and digging without collapse should still be well possible without risk even in lose ground just like in a16. As long as you support the layer above there is no problem.
I did some calculations in A14 and they are still valid today.
According to the SI ratings for stone, if you have a ceiling of stone that is four layers thick and your support columns are no more than five spaces apart you'll never have a collapse.
You don't need 4 layers of rock, three will do actually, but sometimes you find Iron overhead and having an extra layer lets you poke holes here and there without any problems.
I also like to make my columns 2x2.
I know it wastes a bit of rock but I can mine a column if it's got iron in it without losing support.
I pick at it, take the iron, replace the hole.
Same SI in A17 with regards to stone so it should work.
So far... at least for me, it has.
What I'm surprised to hear is that people are getting collapses who've been mining for hundreds of hours in A16.
Clearly then know what they're doing so....
... I'm a little confused.