This project is strictly a low-tech production. Today I roughed out the drum with a hand file while the drum was turning. With careful use of the file, a good pair of calipers and an accurate steel rule I was able to get all of the flat spots off - I started with 23 octagonal pieces of MDF glued together - and kept the diameter between 4-1/32" and 4-3/32", all by eyeballing it and careful use of the file and calipers. This will make taking it down to 4" in diameter much easier, and the sanding time tomorrow will be considerably less. The Mitutoyo dial indicator (bought used on eBay) arrived in today's mail as hoped for. The price was right, and it works perfectly, so I'm about right on schedule.
I've shown the tools that I used - not many and not too costly as all were bought used and in excellent to new condition. The little table saw that the project is sitting on - I got for $25, and it works like a gem - just needed cleaning and a couple of drops of oil on the blade raising and lowering mechanism which was frozen with "gunk" :-)