The other key piece of advice is that you must have a portable grinder to remove the welds from the bottom (playing surface) of the tank. Unfortunately, the tanks that I bought were made by an overzealous welder during manufacturing. Each weld (four all together) was about 1/2 of metal attached to the tanks. I ground the first tank with a file - needless to say it took over an hour and a half...
The next day, I borrowed a portable grinder (the type used for autobody work) from my brother in law, and I was able to grind the remaining four tanks in under an hour total. The trick here is to not let the powered grinder dig into the surface of the tank to produce any 'channels'. It's impossible to clean those up, so stop short of the final grind and finish with a file.
In the meantime, I discovered one new tuning idea with Dennis Havlena's original tuning configuration. I had emailed Dennis after my first build, because the highest two notes (the C and the F, next to the low D "ding" note) didn't have great ring or sound. My theory was that they were too close to the center, and didn't have a stable base to ring appropriately. Thus, I theorized that moving them outward from Dennis's original plans would make them sound better. Indeed, my first drum that I built this weekend, I moved both of these notes out towards the perimeter of the body by almost an inch. The result was perfect, with both of these notes provided much better clarity and ring.
Here's an illustration of Dennis's original configuration (in D Minor Pentatonic)
The second drum that I built this weekend has a different tuning, still in the key of D minor Pentatonic, but with a different configuration of notes that I had proposed in my prior Blog posting: http://foundmusic.blogspot.com/2008/05/how-to-improve-your-hank-drum.html
The notes are (lowest to highest):
D F G A C D* F* G* *octave
The drum which I made using the following configuration came out really nice. I'll post pictures and a YouTube video, as soon as it final tuned and finished (Iater this week). The different configuration of notes has a different vibe. I think that it brings out different songs, and since it matches the tuning of a Native American Flute, it'll be really nice to play along with.
Link to Dennis's plans: http://www.ehhs.cmich.edu/~dhavlena/for-webpage-lp-hang.htm