Hmmm, I dunno IO540. I think the rules of thumb are OK for IFR where all you really need as an idea of an initial heading to steer to hold a radial. But for VFR it maybe 15mins before I can get another fix. I prefer to be as accurate as poss rather than introduce more approximations to the process. Maybe, once I have a decent number of hours under me belt, then I will feel more confident with just the RoT methods.