PaneledFloor

Hey I'm working on this paneled floor that is going to be pulling towards attractor points, and I'm looking for a better way to produce a varying grid.  Right now I just have the grid being divided in the U and V with a number slider, but I want the V to have varying lengths to better break up the pattern of the floor panels.  The random shuffle is an option but I would like a way to lock the U lengths.  Any suggestions would be greatly appreciated.  Thanks.

-Cameron