While the progress on boiler modification is moving at a fast pace, I sprayed the model with black primer to see if there was any obvious defects on the shell. So far, it is better than I thought and touch up will be minimal.
My next challenge was installing inspection and clean out plugs. I had two choices: buy expensive brass parts that don't look like the prototype and are oversized or make them myself. I went with the Red Green's second option as you can guess.
I made the plugs with a combination of holes and 0.040" styrene rod. I first drilled a small pilot hole in the shell of same diameter as the rod.
Then, using a 5/64" drill bit, I enlarged the hole surperficially to create a small recess in the boiler jacket.
Finally, a piece of styrene rod was glued into the small hole. The rod was extending from the surface and was later cut flush with the boiler using a X-Acto blade.
Sure, it lacks the typical rim around the plug, but on many older pictures, it is almost undiscernable. If one would want to make more detailed plugs, I would advise to make the parts independantly, then drill the boiler and insert the plugs. The plugs could be made out of a sprue or a styrene rod with a diameter slightly larger than the largest drilling bit used to shape the plug. Follow my original instruction and you will soon have cheap and easy to install inspection plugs.
To be noted, I also drilled the stanchions mounting holes according to the prototype and enlarged the cab windows. There are still a few holes to drill and running boards to mount.