Not Exactly Sure What You Are Trying To Say - I Know - Hard To Type!
If I Understand You Correctly It All Depends On The Application.
Ext. , Int. , Substrate ect.............
If By Leave It Like It Is You Mean "With Backing" (There Are Buttons For With And Without Backing) This Is Usually Best (In My Opinion) To Prevent An Ugly Adhesive Line When The Vinyl Shrinks (And All Vinyl Will Even The Best Cast Will Shrink A Small Amount Over Time) But You Have To Watch When The Outline Color Is Darker Than The First Layer Or The Dark Color Will Show Through, And This All Depends On The Opacity Of The Vinyl You Are Working With At The Time. But Sometimes You Do Not Want The Build Up Of Layers Either!!??!! If Outside Application You Should Want A Backing Or A Small Overlap.................. If I Am On The Right Track Let Me Know And We Can Discuss Further...........So Much Typing (Hard To Explain With Out Lots Of Typing) If I Am Totally Off Subject Of Your Question!!??!!
I'm gonna take a shot at this because I *think* I understand what scmbag's trying to describe.... I had the same prob, being self-taught on Flexi. Stewart's got the idea there.
You're describing cutting letters that have an outline. Sounds like you're trying to determine how to cut the letters themselves, and then the outlines themselves, and you want to make sure that the letterforms and their outlines line up perfectly so that there is no sliver of background showing through?
The answer is simple and saves you LOTS of work. It did for me.
When you create an outline, the Design Central floating palette shows a tiny button, either red with a black outline ("with backing"), or black with red outline ("without backing"). The state of this button determine whether the outline is a true outline, only existing around the outer edge of the letterforms, or whether it is an entire solid background behind the letterforms.
If you create outlines With Backing selected, then it is an easy task of cutting the background vinyl (the outline), then cutting the foreground vinyl (the letters), and laying them down in a 2-layer stack onto the substrate.
If you add a shape, such as a small triangle, at each end of the lettering, and cut it out with both layers, then you can use them as "line up marks" when laying the top layer down on the bottom layer. This way there is no question about making it line up perfectly centered. Afterward, peel them off and you're done.
I would add to this that the "color trapping" feature is useful here as well.
If what you want is for the lettering to appear outlined from both sides, or to allow light to pass through in a backlit application, then do a simple outline. Then select both the letter and the outline and color trap it. This will create a cuttable outline in one color and the letter in a different color while providing a small overlap.