Personally, I don't think there is a problem with having a fat cab... I've almost finished my cab and it's not only fat but short too. It's like the George Costanza of arcade cabs!
But I like it because it serves it's purpose well, which is to allow two people to sit (on normal chairs not stools) comfortably next to each other and be low enough to turn into a normal TV stand (the TV flips up to a vertical position).
One of the things I like about scratch-building arcades is that you can customise the design to whatever suits your purpose, a lot of purists want to match what they experienced in the arcades but I like the opportunity to make something that is not only my own design but has things that couldn't be done in the arcades... imho cabs are generally skinny because floor space in a commercial arcade is at a premium and that constraint is not such an issue at home.
Here's a sketchup image of my cab, I forgot to add the width dimensions but the cab is 80cm wide, the TV mount is 90cm and the control panel is 1m (But in the end I knocked it down to 90cm)... I think you'll be hard pressed to find a cab who's width to height ratio is worse than mine!
BTW, I'm using a 27" TV and you only sit about 60cm away from it so you can really immerse yourself in the experience!
