I'm not sure if this is the right place for this. In the blog item posted on deadlocks.
I did the same on my van. However the lost key issue was solved by a combination car key safe.
Hidden & locked under the van, in a plastic bag. After four years I just checked it & it's still OK.
like this,
http://www.the-bodyboard-store.co.uk/key-pod-5g-lock-box-combination-car-key-safe-1126-p.asp