</font><font color="blue" class="small">( Does anyone here have practical experience with a tracked skidsteer loader? Can they handle serious inclines?
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No, they can't.
They are too narrow and two short ( in length ) to be stable on any serious incline.
As they say on the Gran Prix commercial, wider is better.
Your best bet, imo, is a 4wd cut with the wheels set to their widest track setting.
You may have to go with ag tires/wheels to get that ability some of the tractors I have seen that come with r4 industrial tires aren't adjustable ( r4 tires are on one piece rims, where the ag tires are on split adustable rims,my Kubota ( ag adjustable ) and my FIL's NH ( r4, one piece rim ) are this way ).
I think 30 - 50 hp is plenty, it doesn't look like you will need a huge amount of hp for just some grading and trail maintenance.