There are 52 increments of 0.1 seconds in 5.2 seconds. 65 ft/52 increments is about 1.25/increment, so if you shorten the lines by about 1.25, you gain about 0.1 sec, or about 0.08sec/ft. 5 minutes and 10 seconds has 310sec/5.2sec equals 60 lap equivalents, my term, so you would save about 60 times 0.1 or 6 seconds/flight, or 1 lap gained/0.1 saved. Sorry for the math, but just trying to show how it works. If not correct, I am sure someone will correct.
That is a reasonable approximation to try, and yes, I did that to save battery for a while.