I run a commercial mowing operation with my MX and 8' mower. To the tune of 300-400 acres per year, ranging from half acre lots to 30 acre fields, but averaging somewhere around 4-5 acres per job.
I have learned in 8 years of doing this, that there is no one mowing pattern that is most efficient for everything.
One job of a few acres that I do, that is roughly square, I mow around the perimeter 3 passes then start zamboni pattern. It is the FASTEST way to get the mower back into the cut. And the penalty for guessing wrong on how far to move down, isnt huge, cause at this point, after outlining the field, its maybe 300' to run across. And at 6 mph.... That takes a whoping 30-35 seconds. So if I guess wrong and my last zamboni pass is only cutting 4'.....eh....only took 30 seconds.
Another job I do is a 12 acre field. That is roughly 1200' on the long direction. So takes a few minutes to make a full length run. So rather than zamboni, I just mow down and back, similar to how one would mow their lawn with a zero turn to stripe it. Because the few extra seconds to reverse and line up for the second pass, is more than offset by the potential consequences of guessing wrong with zamboni.
Then there are just odd shaped fields that neither of those patterns will work on. On those I just continue circling the perimeter until smaller areas are naturally broken off from the larger chunk.
With a 15' mower and 5-series tractor though, it may be entirely possible to do a 180 degree turn within the width of the mower. I'd make a few passes to clear the perimeter, and mow down and back, even if it means making a wider turn at the end.
the penalty for guessing wrong on a zamboni gets worse with bigger mowers. make that final pass with a 15' mower only mowing 1' that was missed is alot worse than missing a foot with a 4' mower