After consulting with Ron Brese about the issues involved with cutting away material from the sides (especially around the lever cap screws) he assured me that it would not pose any problems, so I decided to go ahead and make the cuts.
First step was to apply the pattern to both sides of the plane body. The blue tape was used to position the pattern, then hinged out of the way while I applied 3M Super 77 adhesive to the back to adhere the pattern. Then I filled the inside of the body with a temporary infill. This would stabilize the side walls during the sawing process.
I then sawed almost to the line with a 24 tpi hacksaw.
I didnt try to do both sides at once, but rather sawed at an angle from one side, just starting the cut on the opposite side.
I removed the waste between the kerfs with a fine jeweler's saw.
I sawed one side at a time. There was enough flex in the blade to not cut into the opposite side.
Here I've cut all the waste away.
I started filing the sides close to the line using a flat file and a round file. I took the rest of the waste away and refined the concave section of the curve with an oscillating spindle sander using a 80-grit 1/2" drum, followed by a 180 grit drum. I refined the convex section on a 1" belt grinder using similar grits. After the shape was to the line, I further refined the surface of the curve with some 400 grit paper wrapped around a small square file to keep the surfaces square and flat. I purposely left the flat section, which will be flush with the bed, a bit proud of the final position. I'll file this flat area flush to the infill after the rear infill is fitted.
The dip behind the front bun makes extracting shavings comfortable. I can get my finger in there quite readily.
I think the curve looks pretty good too.
There is .155" of material between the curve and the lever cap screw. Ron assured me that this would be fine.