I'm happy with new or using existing with a rose joint at the point but I would let them come up with the options

Cheers

A new method of adjustment maybe butter once fitted but maybe more work fitting it than adjusting existing system.The shim thickness can be calculated in the same way the camber at the wheel can be calculated for 1 deg neg camber if the wheel is 450mm high times 1 tangent =7.854mm so you need about 8mm packing on your spirit level held against wheel at top for spirit level to read vertical. if you do the same calc but use distance between top and bottom wishbone gives about 4mm per 1 degree so 1mm shim will give 0.25 deg adjustment these figures maybe wrong please check for my mistakes but may help to get adjustment somewhere near first attempt

Has anyone heard anything more from zcars regarding the adjustable from arms?

Not yet Colin, but I plan to take it back to them to work out how to do it when the car is on the road. TBH I've been talking to Dave Gallop at track developments about the same and he's got some good ideas (incredibly knowledgeable bloke) so he may get the job when he's doing my ARB's.

I'll keep you posted but it won't be until summer time probably.