Multi-monitor seamless switching

I've just installed a trial of Multiplicity but I'm struggling to get it to work properly with my setup.

My primary computer has its main monitor in landscape mode in the middle with two other monitors to the left and the right, both in portrait mode. Crucially, the bottom edges of these side monitors are below the bottom edge of the main monitor - so it's a sort of H-shaped display.

I put my laptop on the desk beneath the main monitor.

The problem is that in seamless mode I can't move down from my main monitor to my laptop. It only works if I move down from the left or the right monitor.

Is it possible to get Multiplicity to work nicely with this setup - i.e. so the mouse can move from my main monitor to my laptop?

Thanks