That's right folks, a Bastion - the logical progression from my Tyranid Aegis Defence Line. Of course if I do the Bastion then the logical next step is a Skyshield Landing Platform and then a Fortress of Redemption but lets not run before we can walk.
Occasionally I'll draw myself a little sketch of what I'm after and so my first attempt tried to match the proportions of the existing Imperial Bastion but this is going to be completely scratchbuilt. I'm all for Tyranid infested Imperial terrain but a completely scratchbuilt affair holds appeal for me because it will be unique, match my army, be a challenge and will cost me nothing [importance not in that order].
However, recently I've seen a variety of Xenos bastions that use the GW moonscape as a base and as I have a couple of spare pieces I thought they might be a potential stepping stone. So this is the revised concept sketch, however mounting the 'heavy bolters' on it's compass points will be difficult given the Chitinous towers already situated there. What I may do is make the towers sit slightly angled opposite each other that way the left and right weapon can be in the East and West positions and then the North and south guns will be asymmetrically opposite, one in the right hand Southern wall and the other in the left Northern wall. With 'sphincter doors' [as seen in Advanced Space Crusade] in the left Southern and right Northern.
Taking advice from isotope99 I went for the bigger crater so I have more room to work with. This is the skeletal beginnings. You can see the height to the roof is 150mm and then you have a 20mm wall that will go round the roof with some ridges that will add a centimetre up to the 180mm max height with the Tyranid Capillary styled towers that form the compass points.
Next up I'll be adding the cross-members and probably be cutting slots in the crater base so that I can have it glued straight to the mounting card base underneath. Then I have to decide how to fill out the gaps between the frame and how to create the Capillary Towers. More details and pics on my blog.