Cal looks kind of, excuse my baby language, icky. XD
It might just be I'm used to reading your name around here as Kal, it looks cooler to me.
Cal Tyler looks more well-mannered/soft/professional?, Kal Tyler looks cooler. Sort of more exciting? haaa.
That's just my opinion. Whatever you feel fits, fits.
If you do drop your last name, would you be picking a new middle name, or just dropping middle names altogether? Kal Nichols looks pretty much as good as Kal Tyler, in my opinion.