I have just fitted new discs and bearings etc the kit comes with a machined flat washer about 4mm thick which is to go behind of the castellated nut .Problem is when you use this washer you cannot get a split pin in the hole because the nut is out too far.I have left the washer off and tightened the nut to 150 FP.Anyone had this problem ?
Allen

The fat washer is used to seat the drive flange on the cv shaft
once the flange is seated the flat washer is removed and the split tapered
washer is put on and torqued up
so yes you have it right

Shouldn't it be a cone split washer for the larger Cooper S CV joints? Haynes refer to a flat washer for seating the hub bearings, which is then removed and the cone type fitted (FAM9270).

Yes cone washer , tapered washer
you can use the flat washer to push the cone washer in square
if you like