Scotty - - - looks like we finished about the same time. You are a few stumps ahead of me. Good job!
My gear box is a speed increase type. Ratio is 1 to 1.46. Bought it on ebay and it seems to work - - - never can tell about stuff from ebay. I used a
#100 roller chain and sped up a little more, 17 tooth on the drive and 11 tooth on the shaft. Running the tractor around 2100
rpm (2400
rpm is used to get 540 at
PTO) works best. I have found that the grinder has a tendancy to pull into the stump if you are taking too big a bite. It can bring the tractor to an immediate stop - - a little scary. Just like any new piece of equipment I am learning as I go. No damage done so far - - - except for stumps

.
As for tooth placement. I have 6 sets of angled Greenteeth (700 series)spaced evenly 60 degrees apart around the wheel. Then I have two sets of straight teeth 180 deg. apart. It shows in the picture and gives the impression of odd placement. I was told but the salesperson at Green Mfg. that the straight teeth were needed if I wanted to grind straight down into a stump rather than come from the side. I saw the same tooth placement on a Vermeer SG 252 so I figured I should do it too. Can't say that I have needed them but it was easy to drill a few more holes when the wheel was on the mill and would be difficult to drill later.
Thanks for kind words,
Reggie