hey guys im just working on a few concepts at the moment... and it would be great if you could create X amount of air units at location... stacked! is this possible?

Nope.
Create as much as you like at the location and then order them to go to the location they spawned in.
EXAMPLE:
Conditions:
(Any)
Actions:
Spawn 10 wraiths at Location One
Order all wraiths at Location One to move to Location One.
Preserve Trigger.*

*Isn't necessary.

Zerg air can be stacked via morphing a preplaced disabled then enabled larva unit sprite into said air unit. They won't have a collision box, but they will drift.

I got preplaced scourges to stack too, but I think it only works intermitently. Also, if you morph into a scourge/zergling, only one will be stacked.

If you use the move unit action on any unit which has no collision box, they will stack, but if they do, they will reset, even if "stacked" via ciara's method.