Firstly I'm not a fan of 6 long studding. It never gives the correct torque down on the head.

Secondly I believe the cometic head gasket is not up to the job. When I worked at Jaguar I spent a couple of years working on head gasket design and can tell you that after examining the design of the cometic MLS gasket it is poor and not "proper" head gasket technology. (i.e. is not designed or manufactured using the latest technology of MLS but uses a very cheap method of construction)