Exporting fbx from 3D coat, all retopo objects appearing as material layers in Substance

R0mbag

Hey guys, I'm wondering is it possible to merge all paint/retopo objects in 3d coat? as when I import into substance , each layer has it's own material which isn't really optimal for putting it into a game engine, as when it exports I have a normal, roughness etc etc for each layer.

Any help would be appreciated!