I couldn’t think of any reason to keep the frame pan underneath the frame now that the bearing guides are in place. So, I took the jewellers saw and hacked it away. Now the frame begins to look like a locomotive frame.
Inspired, I ferreted out the 3D printed ash pan and tested it for fit. Despite having accidentally sawn off most of the nubs on the back of the firebox that hold the rear up, the ash pan worked perfectly. It’s such a cool little part, I had to snap a photo, even if it is wrong.
Pembroke:87 
Don’t know if you know this trick already with 3D printed parts, but I dip mine all into “Future” aka Pledge. The self leveling feature of it fills in all the tiny layers of the print, and often makes for a better casting (if making a resin copy). That same idea of filling layers would work here too, to get you a smoother primer layer.
Craig
Thanks Craig. I’ll have to give that a try. The ash pan shown here is a sacrifice part for construction purposes anyway.