Cocko
Oh Dear..
IMO, if it is cooling fast enough to limit isomerisation then it possibly isn't staying hot long enough to get the antibacterial(?) heat treatment that is desirable in the method.
So how long at what temp IS ok to cube with? If the wort is going in at near 100* than how long does it need to play the critical part of sterilising the cube?
I would assume a minute if not seconds... a truly, un educated opinion on that but maybe some one knows?
Maybe 4x 5L cubes is the future.
Good work BG.