Originally Posted by Joscelin V.
Is it just a matter of tweaking the heightmin and heightmax values to have the transition happen in a specific area? If so, then I'll play with the values
In this case yes, since it's a simple stacked map. Basically, find where you want to transition in game, take a /loc and use that value for the heightmin of the upper floor / heightmax of the lower. For more complex maps where you have multiple on the same z-range (eg, a submap for a cave system) it gets more hectic (SS croc caves are quite complex).