WQFN148 Usage Restriction -- 32 mil PCB thickness

We're using an EP4CGX15BN11C7N Cyclone IV device in a WQFN148 package on an extremely tiny board.

The mechanical definition document states that the part shouldn't be used in boards more than 32 mils thick. I've never heard of this kind of a restriction. Normally thicker means more rigidity, which tends to mean better mounting reliability for QFN and BGA packages. See http://www.altera.com/devicepackaging/04r00350-03.pdf for a package definition.

The part footprint is extremely challenging to incorporate into a layout. We'd prefer not having to go to an excessively thin laminate stackup.

Does anyone know the reason for this restriction?

Does anyone have a known good Pads layout decal for this part? (very time-consuming part to design).

Thanks