Whatcha need?
-> Brawl Box (these are the one's I use for stage editing: .73b and .75b, but all version "b"'s and above are cool. After .71, you get a bunch of symbols that help you find stuff easier)
-> A stage, I'll be using Theytah's 20XX Rainbow FD for comedic purposes: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=207651 (http://forums.kc-mm.com/Gallery/BrawlView.php?Number=207651)
That's it, lets begin!
Part 1- Where are the boundary settings and how can I preview them?
Well firstly, you need to open your stage in Brawl Box. You need to look, in the jumbled mess inside these .pacs a model that is usually called "StgPosition". Modders are usually kind enough to store them in the last few "ModelData" folders:
(http://i.imgur.com/bxTTIcn.png)
You know what it is, so keep in mind this... you really don't need yo touch it, since previewing it shows everything blank. Instead you need to preview the main arc file.
(http://i.imgur.com/Pwfz13N.png)
(http://i.imgur.com/MrFgmIv.png)
So after that you might need to enable the following data.
(http://i.imgur.com/DzSfWHa.png)
Zoom out so you can see the whole thing.
(http://i.imgur.com/kz9UonF.png)
You see a bunch of pretty circles and rectangles now, I'll briefly explain what they all mean.
Blue: Is where the camera never goes, it stops following the player and instead shows the player through a scope.
Red: You die if you touch this.
Green Spheres: These are the spawn point of your characters in a beginning of a match, these need to be close to a floor or other wise it will show red instead, meaning the character will glitch his or her entrance.
Gray Spheres: This are the item spawn zones. Items spawn out of it. Cool. (in this stage is not shown must be a small visual Brawl Box glitch)
Part 2: Edit them Boundaries
So, what can we do with FD? Well, for one, I am annoyed that Fox's upsmash kills me all the time. So lets boost the sky box!
First select the "Stg Position" model on the tab above and open the side window.
(http://i.imgur.com/iX9wnb9.png)
(http://i.imgur.com/5fsqTda.png)
Now lets find the dead zone for the ceiling!
The bone responsible for it is named "Dead0N", fitting name.
(http://i.imgur.com/PF4qgRP.png)
Open the bottom window
(http://i.imgur.com/FQL2LLJ.png)
This tells you the current location of that Death line, lets rise it up juuust a bit.
(http://i.imgur.com/8Tep0Oi.png)
Perfect! Now Fox can't kill ya with that annoying Up smash. You see I boosted the "Y" coordinates by small amounts.
But, I'm also annoyed getting kneed to the side death boundaries. So lets boost "X" a bit as well.
(http://i.imgur.com/4MkuqMb.png)
Nice! But its now uneven... better fix the other border then!
The other border is called Dead1N. Lets do the same to these coordinates!
(http://i.imgur.com/LwtWEDL.png)
But, I realized that I would like to see my character flying from the great beyond! So lets fix those as well. The name of these coordinates are CamLimit0N and 1N.
(http://i.imgur.com/CpUDeOd.png)
Lets give the camera guy some more work, he slacks alot.
(http://i.imgur.com/lJ8VQac.png)
Good, now do the same to N1
(http://i.imgur.com/s8kUU1D.png)
Peeeerfecto! Now your characters and the Lakitu have more space to work with. Save the settings and test.
(http://i.imgur.com/hMeGjZc.png)
Perfect!
(http://i.imgur.com/Wr1wVhP.png)
Perfecter!
(http://i.imgur.com/scFO30S.png)
Perfectest!