Looks like the conversion went smoothly. I tried to use the cornstarch trick, but found that it dried up quickly on the sides rather than in the middle. Assuming I had nothing to worry about, I measured straight down the middle from the back 9 inches and began to drill. Nothing was damaged and proceeded with making two holes on the side just above the hump in the inside for the Co2 lines. I want to find some fittings for the outside so the holes on the side look nicer and are more snug, but I"m pretty proud of the results.