I can tell you from personal experience, the 4-way and spinner are too far of a reach. It's nice to have it centered, but I found it more comfortable to be just above P1's buttons. Also, you might get some conflict between buttons 39-41 and P2's joystick if your panel is not sloped. Having those buttons in-line with the 4-way joystick but above P2's buttons could be an option. I also agree with Green Giant, 4 buttons are all that is needed on P3 and P4.
One thing to also think about is ergonomics. Many layouts force your arms to both come in at angles, like an "A", and your wrists are then always straining to point towards the top of the panel. I am a big believer in keeping you wrists straight for best comfort. For instance, on my control panel the layout is designed for the left arm to be vertically in-line with the joystick. The button configuration is designed for an angle hand, yet allows me to have multiple possibilities, e.g., Street Fighter, Mortal Kombat, NeoGeo, Stargate/Defender, etc.



Regardless of what you do, I would highly recommend cutting it out on cardboard before cutting it out on wood. You will always find "gotchas" that you did not even consider when designing on software alone.
I hope my information helps you out on your design and good luck with your project.