Chris,
Welcome! Great looking machine you have there and a nice place to use it. I've always really liked the square-jawed styling of the old 90 series.
Regarding your question about safe side slopes, I am using a 2520, so I can't answer for other types of tractors, but I regularly mow a 20 degee side slope and feel "relatively" safe doing it. I always keep my rops up (not an option for you) and my seat belt on for the side slopes. I do it very slowly and keep a close eye on what the tractor is doing, i.e., if it starts sliding sideways, I slow down even more, and am ready to stop or raise the rear mower a little (to get more weight on the rear tires) at any time. I think the key word on operating on slopes is slow.
The other thing I've seen as a key factor in slope stability is keeping the loader (or any other kinds of loads) as low as possible. I would never even try carring a load in my loader bucket on my 20 degree side slope.
Hope this helps a little.
Just one question from a newbie: What's a "pig pole"?
Best of luck.