PanzerJäger 1 conversion

My frustrated attempts at getting a PanzerJäger 1 in 15mm scale has led me to desperate straits, so much so that I've started designing a fighting compartment and gun conversion kit to be 3d printed, to go on a Minairons Panzer 1 model.

Building it in Blender is pretty straightforward, but I'm hampered by the fact that I don't have a 3d printer of my own, so I'm having to gamble that my measurements are right. Getting beta models printed and shipped by Shapeways is a lengthy business.

Here's the FUD material render from Shapeways;

The module is available for sale at http://shpws.me/OMk3, but it should be noted that I haven't yet been able to print it to check for fit on the Minairons kit.