That's something i fancy doing, although not for a couple of years.
And yes, you must be bonkers
I know, from what other people on here have said, that Chris Crosskey uprated the axle before his attempts.
I'm not 100% sure, but he might be attending the C5 event at Brooklands in January, so might be a good chance to have a chat.
Would it be 2 of you sharing a C5 with a supprt vehicle, or are you using 2 C5's ? Good luck with it
Daz