I've got a pair (as far as I can sex them - but I'm quite confident in their genders) that are not quite mature, but I would like to set them up as if they were so that once they do get to sexual maturity they can take it from there.
The tank may not be large enough as it is a 120 but we'll start with what we've got.
I'm setting up some new caves right now (using plastic ribbed tubing like for clothes-dryer exhaust) which should be good for their adult size (basing this on my almost full-sized sailfin) though a little large for them now they are having a hard time accepting them (but I just put them in yesterday).
These are covered with slate (to hide the bright white

Does anyone think the pleco might take to these well? Or should I try something else & give them a choice? (they had slate caves before but my oscars are mating & I was worried about the plecos getting squished - the os already flattened one cave).
I'm going to also add some fast-flowing air a.s.a.p. but the oscars moved into the 'hot spot' of the tank & kicked the plecos out so I've got to go buy myself another air-pump

So how's the cave situation for the first questions then

Nes.