Gosh, hadn't even considered another spelling. Honestly, due any minute and have been through 50,000 names so far! Will consider Caspar too.
There are so many names I like but sound rubbish with our surname beginning with Z. I think Casper would go nicely though.
I loved Casper the Ghost and it was so long ago that the reference will be obsolete in a few years apart from us oldies and the generation before!