If you dont mind, I think Ill make you a base too, how wide is the channel area in there? I think Ill make it with a 1/8inch end mill and leave a fin in the center, how does that sound?
how thick is the thickest peice you can use with that clip? this would end up being 1/4inch+ your top.
I would make the channels 1/8inch deep and leave a 1/8inch base, then probably leave it up to you to lap it
Jon