What is the permissible distance from weather head to roof edge?
Without actually seeing the installation, I'm simply guessing here. They could be referring to National Electrical Code 230.24(A)ex. no. 3.. Which says that the clearance above a roof can be reduced to 18 in. if the service conductors do not overhang the roof by more than 6 ft., and there's less than 300 volts between conductors, and the service conductors terminate at a through-the-roof raceway.

So basically, if the service conductors have to overhang the roof by more than 6 ft., this exception can no longer be applied. Without this exception, the service conductors must be 8 ft. above the roof.

You'd either have to extend the weather head up, to keep the conductors 8 ft. above the roof. Or move the weather head, so that the conductors do not have to overhang the roof by more than 6 ft.. 


  National Electrical Code 2014
  
  Chapter 2 Wiring and Protection
  
  Article 230 Services
  
  II. Overhead Service Conductors  
  
  230.24 Clearances.
  
  (A) Above Roofs. Conductors shall have a vertical clearance
  of not less than 2.5 m (8 ft) above the roof surface. 
  The vertical clearance above the roof level shall be maintained
  for a distance of not less than 900 mm (3 ft) in all
  directions from the edge of the roof.
  
  Exception No. 3: Where the voltage between conductors
  does not exceed 300, a reduction in clearance above only
  the overhanging portion of the roof to not less than 450 mm
  (18 in.) shall be permitted if (1) not more than 1.8 m (6 ft)
  of overhead service conductors, 1.2 m (4 ft) horizontally,
  pass above the roof overhang, and (2) they are terminated
  at a through-the-roof raceway or approved support.