Ahh how much this discussion (and the legend skill system) reminds me of my days GMing Hackmaster 4th. I consider it an *early* percentile based system mainly because it being the first one I ever encountered.
Skills maxed out at 125%, and there is a reason for pushing high skill ability - to negate any negative modifiers you might encounter.
But also you have to consider the RoI of pushing the skill that high especially during character creation. Have you left any room for the character to progress? How did the character get to that level (especially if they are young... an 18 yo with a 125% in Astronomy seems pretty far fetched).
In the case of the "150% vs 50%", this is a serious mismatch of combatants. Is the less-skilled character looking for a fight trying to provoke the better skilled character? Is the better skilled character just an egotistical bully who enjoys fighting only opponents they know are too weak?
In the first case this really is more "how does the skilled veteran teach the young pup a lesson without taking advantage of their immaturity". This should be the classic scene of the young 50% pup angry not knowing when to stop as the veteran keeps dodging, slapping the pup's arse with the flat of his blade, occasionally putting a fist upside the pup's head, and all the while trying to talk some sense into the pup so they'll stop this nonsense.
In the second case its a matter of "do the numbers really matter this is a lopsided fight and there is no real chance for the weaker character to prevail". The fight should be short, sweet, with the young pup on their back sword point at their throat, if not bleeding to death/dead.