Thanks, the ones I have access to are actually crawlers. They are owned by my brother in law, who has been self-employed with them since the '50s. Not actually these, he wore some out, rebuilt others, etc. He is 85, and retired down to about 40 hrs a week. He hasn't ever shown me a chart, he's one of those guys who "if it won't lift it, the tracks will get light". He does mostly ricefield dragline and piledriver work.