I'm not sure if I'm honest. To drive 4 ballnuts without pre-load would be fine I think, but when the ballnuts are clamped together there is an extra load to overcome, and the Y/Z is pretty heavy. Is it worth the risk to have missed steps on a critical job? Not sure.
Decided to leave it like that and put some pre-load between the front and back ballscrews instead.

Sending pm shortly . . .