Compass calibration not possible to do with big rover, what to do?

Hey guys,
im thinking of converting a small electric car ( around 500kg) with ardurover.
how can i handle the problem with compass calibration?
is there a workaround, or tips?

Thanks

Here’s something that worked for us. Start with PH mounted and vehicle pointed North. Start calibration, turn wheel hard left and drive in circles. Then rotate PH as required and repeat, rotate and repeat until finish. Although not dead on, it works.