Originally Posted by Marcus Mussa
I believe the rulebar roll will be strictly enforced. Pre-1961 cars do not have to have a rollbar, which means you will be ok with your 250F. The one on your Lotus 33 will have to be 2 inches above your helmet.
I was wondering whether recent helmet developments may have contributed to concerns about the height of roll bars. It may be my imagination but it seems to me that helmets are slowly becoming larger (presumably for improved protective gap and padding material between the shell of the helmet and the wearer's skull) and that many seem to be worn rather high on the head.
However a quick picture search for Lotus 33 suggested that current historic drivers and Jim Clark in 1965 have about the same helmet height to roll bar height relationship. Whilst the hoops look a little different and the overall mountings seem to have been modified over time, the height seems relatively consistent.
I'm not sure the car would look right with a higher hoop so one hopes it may be possible to lower the driver if necessary.