In my opinion the "square" layout is nonsense, so I totally support your decision to go with the Sega curved. I'm using the Astro City layout; looks like you're using that or similar. I'd recommend adding a seventh button though, four across in either the top or bottom row is good for NEO GEO games and other four button games. Curved vs. square and 6 vs. 7 has already been argued ad nauseam here:
http://forum.arcadecontrols.com/index.php/topic,118842.0.htmlI'm also using the wider spaced joystick placement, and I highly recommend it. I'm even thinking of trying a little wider. Moving the stick closer to the buttons may give space on the control panel, but think about the two people sitting next to each other. The closer the sticks and the buttons, the further in you have to angle your arms. This points your elbows OUT. You'll be bumping elbows more this way. Not so comfortable.
Make the ergonomics of the joysticks first priority, you'll be using them 95% of the time vs. the trackball.
Last thing is that I'd recommend putting the start button closer to the stick and buttons for convenience. You won't bump it, and there's no need to reach so far every time you press start. I put it equidistant from the top left button and the stick, and raised up slightly. I've been using it like this for a few years and it feels very natural. There's a pic of my layout in the thread I linked to.
Oh, just took a lot at your blog. I love how you're referring to that Barry Sheene bike for your colors. I've got a custom 79KZ650B, soon to be an 810.