If the cage has CAMS approval it is permissable.  The RWC side has nothing to do with the dash.  but correct that side intrusion bars are usually where the problem comes from a RWC perspective.
 
Cars already on the scheme are not required to have retrospective engineers certification

Thanks Gareth.

To clarify
from reading the regulations my understanding is as follows
 
currently on CPS and cage is CAMS approved = OK
currently on CPS and not CAMS approved then VSI28 applies
New cage on existing cps car or new cps application requires VSI28 and VASS even if CAMS approved
 
VSI28 is where the front leg becomes an issue
 
 

That is what I had explained to me by the rwc inspector???
For rwc had to meet VS128, and for that it must go through the dash.
I guess it depends on who you speak to, ultimately it's their call and their rwc license.