For some reason they scourges or queens don't stack when I use the disable,enable,enable trick, but when I do hydra's or zerglings they do stack. Well actually air units do stack, but separate after a while. I want them to stack without separating after 10 seconds.

Force them to constantly move to a 1 pixel location centered on one of them. Move or Order works.

But I need them to be able to move the units when the player want them to, but keep them stacked so they don't move when the player does not.

Afaik there's nothing you can do to stop air units to drift.
However sometimes I have seen air units that did not drift in normal games. No special trick, just move them somewhere and then they stay stacked above another. But it worked only for 2 or 3 at the same time, so I doubt that will be of any help. But feel free to experiment in what casees units don't drift.

Move doesn't work. Actually that would instantly seperate them. And if you preserve the move the units would jump around wildly.
Order does the trick. The units will still try to drift apart, but if you order them frequently they will stay stacked for the most part.
If you want to have the units under your control you could make an obs or something as a pointer, on which you center the location. And have a civ selector or something similar somewhere with that you can perform the move to center order.

Yeah, now that I think about it, the move action would make it almost like a mobile grid placement with the unit forming around the one unit, in somewhat of a perfect box.

eh the civ isnt really necessary o.o why not just control the observer if thats the "order" unit but if u use "move" command itll never attack if its constantly that way

I guess I'll use ground units. Whats a fast,stackable, and a ground unit that does not zig-zag when it walks.

An Ultralisk.

Zerglings stack very nicely.

Zergling do stack very well but, they zig-zag which is what I do not want.