My boss is thinking about buying an i Series ZTT42 for his property and asking for my recommendations. ...
Gifix,
I've got the 50" model and use it on about a half-acre yard. In fact the 50" deck was probably overkill for this size yard -- the 42" model would have been just fine, and a bit easier to maneuver and put on a trailer, get through 48" wide openings, etc). There's also a 46" model.
I've got tons of trees too.. in fact leaf pickup was the reason I bought a lawn tractor in the first place (was always a push mower prior to this yard). I drag a leaf vacuum for this purpose (Cyclone Rake). I probably collect about 10 cubic yards of *mulched* leaves each season. A bagger simply wouldn't have cut it.. too many stops to empty. Plus baggers do clog frequently. A used CR is not much more than a new bagger attachment anyway. I got my CR for $550 used, although they're a bit hard to find because people tend to hang on to them.
I did hook up a 42" snow blower to it (among other things). Required some modification since it wasn't made for this tractor but ended up working out.
See the various links in my sig for adventures with these attachments (blower, cyclone, etc).
As for slope, 25 degrees is actually quite steep.. in the owner's manual MTD recommends only doing 15 degrees max with the i-Series. Did your boss actually measure the slope to get 25 degrees or just by eyeball? It's easy to overestimate ground slope by eye.
Easy way to check.. he can use a 3-foot level and tape measure. At 15 degrees the free end of the level will be about 10 inches above the ground vertically. At 25 degrees it will be 18 inches off.
Regardless, the i-Series is a good hill climber and very stable given it's low CG and wide track. And if he's wants even more stability he can add weight like
gcbailey did with his Cub GT. Turf tires and chains work well for winter traction, even better if wheel weights are added or the tires are loaded.
For general reviews of the i-Series, try
this thread, and
this one.
Come back with any questions.. I'd be happy to comment further.