Seen both of those projects...Transformarcade is really too slim to look like an authentic arcade (although its cool in its own way). And mobile mame is not much different than my existing bartop/mini cabinet...looks very similiar.
The best way to proceed is to start construction I guess
Good call on the seams and I might revise that aspect...
Just a quick note: the other thread is about Transformarcade, the animation you saw is my yet-to-be-announced FlatCade project. Transformarcade is actually a Transformers-themed cab. It's just that, like some people in that thread, we thought it would be a transforming cab so that's why I put my animation in my reply.
And yes, that version of FlatCade really is too slim and that is one detail that I have since corrected.
Indeed, Project: Mobile MAME is very similar to your Final Fantasy 3 Piece Bartop, but it does have some built-in features that, IMHO, make it easier to move around (wheels, handle in the back, place to store the control panel, etc).
One suggestion I would make is to go LCD for your project. It would lower the weight and make it possible to leave it in place, making the whole thing a lot simpler IMHO. With an LCD monitor, an upright is probably more than 80% empty space.
I don't know your computing requirements, but the most recent mini-ITX motherboards are really quite powerful, allowing you to have a complete computer in less than 4" height.
From the tests I did in Sketchup, you should be able to have roughly 6" thick modules at the most. The LCD monitor, control panel , computer and coin door/mechs all easily fit in 6" depth (if you tilt the CP vertically, 6" is more than enough to clear the total joystick height).
I can't wait to see your take on the portable upright idea!
edit: this is what I was talking about for going around the seams problem: