[UA] minimum rolls question

[Tim Groth]

I think the idea is as follows.

If you are doing something tricky it can give you a greater benefit,
and in fact must mechanically to make sense as a successful
performance of the action.  A downshift represents a penalty, outside
conditions that hamper your total chance of success as well as
limiting how well you can do.

You could, conceivably, set up a general scheme in which a +10 minimum
gives a +5% shift.  Meaning, you can try tricky stuff for greater
potential gains at an overall increase of the chance of failure as
your lesser efforts don't cut it anymore.