Hi,
The answer to all of your questions is what actually feels most comfortable to you.
- What the standard 4 player control panel slope is?
I know I will make my CP flat because I'm a little taller than average and a slanted panel puts more strain on my wrists. I've read similar topics here and people make their CPs slanted up to 15 degrees:
http://forum.arcadecontrols.com/index.php?topic=92818.0- How high off the ground it sits on?
This measurement should be adjusted to your height. I found my sweet spot by putting books on the kitchen countertop until my hands felt most comfortable. You may also visit jakobud.com, download some classic arcade cabinet plans and get the values from those...
- the dimensions of a good shaped control panel?
The dimensions of the CP depend on how big you and the other players are. If you put each player's controls too close to one another, playing will be uncomfortable.
Also, do take into account the viewing angles of the monitor you plan to put in the cab so that the outermost players actually see stuff.
I would suggest you to browse this topic to gather some ideas for your CP:
http://forum.arcadecontrols.com/index.php/topic,59359.0.htmlCheers,
s4