For club sprints you don't need a cage, but if you
have one installed it must be cams approved (logbooked)

It might sound silly not to be allowed to run with
with a non logbooked cage when its ok to run without
a cage at all, but the rule is there for scruiteneers to
refer to when people show up with home built cages
with bars dangerously close to the drivers head etc.

One scruiteneer told me he'd even seen a car with
a chopped up trampoline base used as a roll cage!

That said, at the end of the day its up to the club
scruiteneers on the day to let you run your car or not