Can I decline to take the benefit of a "Double Prize Loss" or a "Quad Prize Loss" penalty given to my opponent?
No, it simply changes the number of prizes needed to be taken to achieve a win condition. You and your opponent MUST sign any required Prize Card Penalty Slips, keep track of the new number of remaining prizes needed to win, and anything else necessary to implement the penalty.
Source: TPCi Rules Team (2018-04-26)