Control Panel layout help, 7th button for fighters?

[Burn4Evr]

I've been lurking on this board for a while and decided to create an account and ask a few questions
I've been trying to create a basic layout for mame cab, thought I had it all figured out.... til I saw a 7th button.
I was going to go with a street fighter 2 layout (possibly modified to curve with the hand, still debating) I was just thrown for a loop when I saw a 7th button on some CPs to the lower left of the 6. I was wondering what games use it, and is it very important?
Also I was wondering if there were any really good games that used 8 buttons, I see that there is the choice to use 8 with IPACs but didn't know if it was worth actually fitting them on

[xmenxmen]

Most that have the 7th button use it for neogeo games.  Some will tell you to add it while other say it's not needed.  It's really up to u.  Neither of mine has it.  the 6 button sf one works fine for all games.

[PsychoAU]

I have the 7th button.  I use it for Neo Geo games and for the run button in Mortal Kombat 3.  Those were reasons enough for me to add it on.

[Green Giant]

There aren't really any games that use all 7 buttons if your were wondering.  It is just to make it cleaner having the bottom four for 4 button games, ie, all neogeo cabs.  Otherwise you would use the bottom three and a top one.

As for curved layout, it isn't really more ergodynamical.  Your fingers curve when straightened out, but when you are playing, you have those fingers bent to get a good hard button mash.  Position your hands like you are actually playing street fighter and place your buttons like that.

[Burn4Evr]

I  just wanted to say thanks to everyone who responded. The extra information helps alot..... now I just have to figure out how I'm going to implement it.... I guess I can always build more CPs =D
The fact that I'm a big fan of Neo Geo... I'm probably going to have to have the 7th button ... hmm maybe even adding the 8th button.
I'm starting to see why people build Franken-panels