One of our members Mike424u is currently trying to replace his CDR30 with an aftermarket system. As part of that exercise he has had to reverse engineer the new Quadlock connector used on the CDR-30 in place of the triple ISO connectors used on the CDR-24.
I have been in contact with Mike and have worked to reverse engineer the CDR-30 pinouts on the Quadlock. There is a one to one correspondence between the pinouts on the CDR-30 and the CDR-24, with one small exception. The CDR-30 has two additional pins for the Aux input, missing in the CDR-24. Based on this it appears to me that it is possible to build a conversion harness that will allow you to retrofit a CDR-30 in place of a CDR-24.
There are two caveats. You will need to code the CDR-30 to work with the earlier Porsche. I do not know if it is possible to code a CDR-30 to function in an earlier Porsche. I would think it is possible, but I do not know. The only other issue I can imagine is will RDS work with the older Porsche dash computer and the CDR-30? Again, I can see no reason why Porsche would have had to change it, so it probably does work. I do know for certain there is no electrical wiring impediment to the replacement.
do you know whether anyone has ever figured out whether a CDR-30 can be retrofitted into an 06-08 cayman with a CDR-24? sounds like the connector can be adapted, but you were unsure about the rest of the system integration (w instrument cluster/etc).
i'm very interested in getting a "used" CDR-30 and putting it into my 07 CS.
I have not done any further work on this problem. You might want to contact Mike424u. I think the only real problem is security coding the new radio once it is in place. You Porsche dealer would most likely have to do this for you. You might want to check with them.