Numerous posts on this if you do a search. IMHO - don't bother. Your Cali can only be stolen if they have/steal the keys or lift it onto a low loader. For the former, keep them safe, for the latter, no defence and about as likely to happen as an unlikely thing that is unlikely.
Most stories of "I know someone who had their van stolen" are talking about vans from before Thatcham standards, or making it up/repeating someone else's story as their own (who also made it up).
For insurance we found some quite picky because of the overall van cost - even the fabled Comfort, who were asking for a lot of money AND a tracker. We ended up with LV - full cover, two car policy with our Tiguan and 1/3 the Comfort price.
*Note - I have no issues with those who fit disk locks etc for their own peace of mind and to avoid thickheads smashing a window because they think they could steal it with two bits of wire and a screwdriver.