Fluent transition from 1 MultiTarget to another

Imagine this:

I have a maquette. It contains several buildings.
For this I want to make a AR app that projects animations (or whatever) onto this maquette, using an iPad for example. Because this is an maquette, I want to be able to walk around it and at all times keeping the animations (or whatever that's projected) on screen and in sync.
A problem that could occur is the height of the different buildings. I thought I could tackle this by making a few MultiTargets with roughly the same dimensions of the buildings.

So far so good. I made a test-setup with 2 cubes and each one is projecting the model at the right place. But the transition between the different MultiTargets is not as fluent as the transition between the sides of just 1 cube. So if I have one cube and rotate it 360 degrees everything is fine. But when I have 2 cubes in view, and cover 1 cube, it takes a while before the app registers the other cube. An unwanted delay occurs.
How to solve this? Setting the Max Simultaneous Images to more than 4 doesn't seem to do anything.

Or should I use 1 ImageTarget per side of the building? As illustrated here:



Tips? Tricks? Suggestions?

 

Try UCS. That should do the trick:
http://forum.unity3d.com/threads/108256-Unified-Coordinate-System-for-String-and-QCAR

Edit:
And yes, put a marker on each side of the cube, unless you find that the marker occlusions (occluded by the buildings) corrupt the recording process. Then put a marker only on each roof.

If you add UCS geometry, you have have objects in the streets which are occluded by the buildings as well.