Agree with all the others, he would be the golden employee, so long as their are no complaints from customers but even his productivity is way down to be called rushing.
You set the daily target, he beats it, he goes home simples
Our guys are on flexi hours, they get the days work sheet and value of the day, they know what hourly rate the work brings in so the total is divided by this, equals the hours working that day, some days it's as little as 4 hrs sometimes 8 or more, as long as they have done over 120 hrs every 4 weeks everyone is happy ( usually they clock in around 160 hrs each
Just a point with greggs. The other Saturday I was in McDonald's at around 10.10, they had run out of eggs and bacon.
Customers had to wait until 10.30 before they would start serving burgers.
So in effect they were closed for 20 minutes.
Perhaps give your quicker guy more work per day and a pay rise
Darran