Depends on the LED in question. There's no point unless they are efficient. A lot of folks think LED is cooler because they cant feel the heat but its just getting dispersed into the grow room quicker, I'm talking cheap LED there.
Those cmh stacked will do amazing I imagine.
I gave my mate my old cool tubes with 600w hps, he runs 2 stacked in the cooltubes in a 1mx1m tent. No problem with temps. But obviously his extraction is set up to go out of the house entirely, not getting churned back through over and over.
Anyway point is he does damn well with them and makes the most use of his space since he had to down grade after moving house.
Will have to keep an eye on your posts, real interested to see a stacked 315 cmh on the go.