Fully welded the tank bottom before tacking the mounts on the frame. The amount time I spent tacking and lining up the bottom, there should be a very minimal amount of movement. But I spent way too long fucking with this tank and all of the mounts, to have it not bolt right on. I will grind the welds flush on the bottom of the tank, then weld on the mounts. 
Welded, fully welded. About god damn time. Some warpage around the the top 2 mounts, but that's the risk in doing it handmade. A skim coat over the bottom and into the transition from the bottom to the sides, and this thing will be ready to rock.
Tunnel going in. Grind the shape of the tunnel and mount and tunnel assembly in the bottom of the gas tank was not that hard, just time consuming and dirty. I hate using carbide burrs because those little steel slivers are nasty, but man do they work good. Rounded over the rear tip of the tank. No special tools, just a body hammer and patience. So happy to see the tank bottom tacked in, so fucking happy...
