Hi Allocator,
Have checked Maps/Airports/Signs etc and can see no options for turning the extended Centrelines on/off. The odd thing is I'm sure the option was there when I first got Radarbox about a month and a half back (RB 2009)! Haven't updated/changed the version (not sure how you would, guessing you download a new version off the website?). Maybe it's just me going mad...
Cheers
Mark