the collars all look to structured for casual short sleeve shirts.
they should have used a softer lining in the collar
they also could use a different button.
they look to much like dress shirts.

Everyone has a different idea of casual/sporty.
the stays are not the issue.
He just used heavier band and collar lining then I would have used, if i made these shirts for my self or a customer.
If you are going to wear these under a  tailored sport coat, then I guess you would want a collar with more body.

We all have different ideas of "What is Hip".  To me, these are old man shirts that you could find in the Maus and Hoffman catalogue, carroll & company, etc.

Atam could have found you better buttons on his way to the bus station!

the white shirt could have used a natural coroza button or a natural (non-White) shell button if you wanted it to look more relaxed.

The red print is fun. I just would have softened up the collar.
the windowpane is just Ugly.  I am not shy to wear large obnoxious patterns. this one has too much white in it to look fun.

Carl

Carl

FNB, 
     This is something I have been toying with a bit in my head lately, but havn't quite had the time to mess around with.  I think this could be a very useful sort of garment for dressing well in casual situations.  I agree with carl that you should really go for a different sort of collar though.  Otherwise it can look like a dress shirt trying to be something it is not.  I always liked the Barbera 1 piece version of the button-down without the top button myself.  The great thing about a bespoke version of the short sleeve is that you can really get creative with all the styling details as tradition does not apply.
     I wanted to ask you what kind of hem/tail treatment do these shirts have.  I would think a vent construction would be the most versitile as the shirt would be clean both tucked or untucked.
     As for fabric, I like you choices.  I think they give you options for a variety of situations.  I think the third check  probably works well for you.  Those are colors that obviously flatter you, and I think that with a little summer color, and especialy worn under a jacket, the white base of that shirt will appear crisp and fresh and will focus attention to your face like a necktie.
     I have been thinking about trying a foulard for under a jacket in the summer.  I thought this might me a younger, and less affected and costumy alternative to an ascot.  What do you think?  If I can get a chance to work on some things for my self I'll post pictures and see what you think.

-Z