I did some more work on the step kit this evening. One of the first things I did was to polish off some of the roughness on the back side of the flange. I could see that that was scraping up the plastic covering and I didn't want the same to happen with the alclad.

Next, I made up a template to fit on the back side of the flange. I trimmed the hole so that the template doesn't have any interference with the fillet weld on the back side.

After drilling the template to the flange, I clecoed it in position on the side skin. You can see that I need to trim away a bit of material around the hole...mostly on the right side.

Here we are after trimming with a burr in the die grinder.

Last thing for the evening was to trim the lower aft corner (in the upper left in this image...remember the fuselage is still upside-down), radius the corners, and deburr it all. I tried to make the trim angle match the lines of the conical bend. I think it came out reasonably well.

You can see that I'm left with a gap on the underside...especially the lower aft corner. I did some research about this last night and pretty much everyone that discussed it on the website had the same problem. It seems the standard solution is to fill with RTV or Proseal. I'll do the same.