If I remember correctly a Mat Pose will not work on a prop as is, unless it's parented to a figure, like say a hair prop etc. MAT Poses will only work on figures! OTOH you can create Mats for props for Poser 5/6 in the Material folder in the Pose room, just save directly using Material Collection option! Hope that helps some!

You can use MAT POSE Edit which you can find in the Free Stuff to create Mat Poses in your Pose Folder!

MS Windows 7 Home Premium 64-bit SP1
Intel Core i7-2600 CPU @ 3.40GHz, 12.0GB RAM, AMD Radeon HD 7770

PoserPro 2012 (SR1) - Units: Metres , Corel PSP X4 and PSE 9