Cut my old cap off with a scalpel. Nice clean cut. No pulling or snapping. I didn't like it, looked like it would break off at some point. I usually have my Valentine 1 plugged in most of the time anyway.
There is a cool cord that you can get for your Valentine 1, that hooks it into the rear view mirror for power. Very clean install. There is a thread on this, probably if you search Valentine 1. I paid the $25 or so to get the cord from the Corvette supplier, but you can also do it cheaper. Another benefit is that it powers down automatically. Well worth it.