Step 4: using a pencil, draw a curved line on each bulkhead as a guide for cutting and sanding the bulkhead to its new shape. Hangar 9 has conveniently made the bulkheads ring-shaped, which gives the modeler an easy reference for drawing this line. For this kit, the line doesn't have to be extremely accurate. Plus or minus 1/16 might even be close enough at this stage.

Step 5: using a razor saw, cut away most of the excess bulkhead. Don't cut right to the line at this point.

Step 6: use a dremel tool with a sanding drum to carefully sand the bulkheads to the line created in Step 4. A sanding block may be used to check the relative curvature of each bulkhead and to do any final touch-ups.

Step 7: use the sheeting removed from the Razorback to mark a series of points on the forward, angled bulkhead (at the hatch cutout). This could also be done with a stiff steel rule, but I didn't have any of those handy. (No crude comments here, please)

Step 8: again using a razor saw and a dremel, remove the excess portions of the angled bulkhead.

The results to this point should look something like this last photo, with all four bulkheads appearing nicely rounded and ready for the next steps.