C) towball mount thule euro for me for all the reasons given above plus,
Its a much better way to secure an unconventional FS frame design with awquard hydroformed down tubes and FS linkages that just dont work with a roof mount system.
If somebody drives into the back of me, its their insurance claim and I get a new bike. If your using a roof mount and forget the bikes are on top, Its you that picks up the bill!
I can remove the towball mount rack in about 30 seconds and I dont advertise the fact I have bikes all year round.
Much happier being able to see and check on the bikes as Im traveling. The wobble on option A, and the poor clamping on non round tubes just scares me.
Obvious downside is the shear cost of having a towball fitted and the racks themselves are quite costly.