Last time I guided at Croom I took out a B- group. I had some B riders with me so we went at a slightly faster pace then normal. I started at about 10 but we finished the ride between 10-12. We did about 15-20 miles by heading south on yellow. Red over to blue and did counter clockwise. All the way up past FR4 where the red connects blue with yellow. We then cut over to yellow counter clockwise to finish the loop.
The B group probably did a 10-12 pace and about 20 miles with less stops. The B+ goes 12-14 and between 20-30. It all depends on weather, terrain, and who shows up and how they are feeling that day.
Croom gets the less amount of riders for the scheduled rides. Something magical about Croom then some prefer to avoid.