Hardball Mainspring Housing Rules

Anybody know if a wedge mainspring housing is legal or not for Hardball? Example, Wilson Combat Mainspring Housing V-Grip.

some match directors might deem it illegal because it is not specifically called out in rule 6.2.1 or 6.2.2 but I do not see anything about the housing that makes it look different than a regular mainspring housing so I think some director's might not even notice it. Your best bet is to email the cmp it and go by whatever they say.