a cooling hole cannot protrude on to the roof line at all. if you need to go onto the roof line at all, so you can get fuel in it, then it must be 30mm, even if its just 1 or 2mm into the roof line. if your tank is accesable from the front windscreen then 60mm is allowed.
Serpent - Walter RC
Serpent E Power ..... Serpent 747 Reds M3T
Serpent 966-TE Reds M7T .... S411ERYX Speedpassion 3.5T, T-Shox
Serpent 811-TE REDs R5T