Brush Grubber BG-11 Brush Grubber Xtreme

what's the smalles diameter this would work on?

Does it come with a chain?

I have a 58hp turbo diesel jd - is this too much power for the grubber? should i go with a heavier duty model?

can I use this on stumps that are only 4 or 5 inches tall, some of the trees have already been cut down and there are only stumps left too big to mow?