Chip,
The system we developed at my club in NJ was incredibly effective.
No rangers, no warnings, no on course confrontations.
No Mulligans on the first/tenth tee.
The clock starts when the last golfer tees off on # 1, the clock stops when the last golfer walks off the 18th green.
The round must be in less than 4 hours AND you can't be more than 8-10 minutes behind the group in front of you.
Violate either and the ENTIRE foursome gets a slow play letter.
Any golfer getting a second slow play letter can't tee off before 2:00 on the next two Friday, Saturday's and Sundays that he's playing.
Get a third letter, it's a month.
Get a forth letter, it's the rest of the season.
Within two weeks times went from 4:40 to 3:50.
And, all but a few enjoyed playing at a faster pace.