About the angel of the joysticks... consensus advice will be don't. Especially this being your first panel and being just two player there is no reason to take the risk (many including myself would argue one never should on the three and four player positions but that isn't germaine). Have up be straight towards the monitor, perfect right angels with no offset and you'll never regret it. I promise you aren't gaining anything by angeling.
What sort of systems are you using, I imagine by the number of buttons you're doing console games as well, which is fine but sometimes less is more.
GBeef's work is primo as always but I would align your top row of buttons with the centerline of your CP, perhaps even a bit higher, right now everything seems a bit low because of the sharp angel of the buttons as well. I'd lose the angle and put them straight across. You're probably worried about bumping player two or something right? Don't be, it almost never happens and when it does it's on purpose... call it a tactical ploy. You'll benefit by more room below than above your buttons, right now you've got some wasted real-estate. Having the trackball a lower can be a good decision but for sure move those buttons up, line up your joysticks right, and align your joysticks with the top row of buttons as well, that trackball will be all but useless with the joystick planted right beside it.
This hobby is wicked fun, looking good so far and with a few tweaks I think you'll have a CP that'll give you hours of fun!