Be interesting to see you work this way round. I did my second ever matte projection in Maya over the last couple of days, but never built geometry first, then painted it. I figure, quality projections probably work much better if you build the geometry first, rather than just using simple cards and planes for hills and cliffs and bits. Having worked the 'simpler' way around for my last two matte paint/projection projects, I figure this 'geometry first, textures second' workflow, is the way to go to push up a gear