Here's my way of converting a standard Land Raider into a Prometheus variant from Imperial Armour volume 2. Since the main difference between the two is the sponsons, I'll start with those. I've started on the different hull front, but haven't finished it yet, so (with a bit of luck) a later post in this thread will detail how I did that part. Making the heavy bolter sponsons is actually quite easy. What you need is the following parts: A Land Raider (duh …); Two sets of heavy bolter spon