I agree Cheyne is horrible & disfigures Shane. I am a little tired of the spelling Shane. Shayne is the spelling used in one of my favourite musician's name: ShayneWard. I also thought Shayne would convert into the nn Chay more naturally.:o)
fair enough...Oops, I didn't realize you were going for the Ch-sound & not the Sh-sound. Silly me. My first suggestion would be Chet, but I guess Chase could work (I really dislike that name).