Hi Pete
Nice to see someone else on the forum who's in my neck of the woods! I've emailed Mross a couple of times but haven't received replies to any of my messages. I also drove out to their location a few weeks ago but failed to find any sign of life. Consequently, I assumed they had perhaps shut down the business. Are they still going?
The box in question was a square one and the owner informed me it was from a radio truck. It felt VERY solid but I'm sure it was also quite heavy. The Unimog carrying it did not have a turbo engine. It was high enough to stand up in (I'm around 5'9" and had a couple of inches to spare), although if you spent a long time in it (as we plan to do), it may have felt a little claustrophobic. However, as you pointed out with the example photos, it could always be stretched in height and / or length.
Cheers