Wagon Extension for Steampunk Tank

I was looking for something to use as a Dwarf Steam Juggernaut for Warlords of Erewhon. I liked this Steampunk Tank, https://www.thingiverse.com/thing:3488130 , but it didn't seem like it was big enough to carry the complement of crew that is listed in the unit profile. I used ecaroth's Dragon Hunters Wagon to make an extended bed that can hold 6 miniatures on 25mm round bases.

The bed is meant to be glued onto the back of of the tank and have the wheels from https://www.thingiverse.com/thi