Yeah, I'd much rather be doing a suspended floor but with a 220mm gap its not deep enough. Plus got no air bricks now its been constructed.No idea about bounce. I’ve only used PIR boards and then it’s only been one layer. The chipboard at 22mm thick and glued, should be quite stiff. I’d just worry about any bow memory in the sheets
How would you sort the flooring if you were doing it yourself? I assume you'd screed it so that its only one layer of PIR?