Despite the splits and not being mounted, it is rock solid, so it should definitely improve stability.
Edit: measured with a ruler, there is no deviation to parallel over the length (within a fraction of a mm). I'll get the verniers onto it tomorrow, but I'll need a straight edge too, as it is to wide.
I'll get it on and see how the stability improves, will likely reprint sometime in the future, but I don't see any urgency as I won't be moving it much.
I am toying with dropping the second deck and just running heated beds straight on top of the tray, as the bilinneal levelling in rc8 is awesome.
Also trying to work out how to mark and drill the holes for the bearings, I don't want to do a hack job (my normal m.o.) and stuff it up.