So just a question…. Are you guys using the vinyl as a masking setup to spray and then removing it to reveal the base color or are you using the vinyl as the finish product?
A factory template allows for repeatability without having to re-measure everything. After the (in this example) stars are positioned on the wing and marked the templates are removed and fine-line tape is used to seal the edges. Then you can either use a reusable mask with masking tape between the fine line and the mask -or- , if it's a one time thing, cover everything you don't want painted and shoot paint.
The masks from Aero Graphics are made from the same mil thickness tape as the 3m fine-line tape so after you locate them where you want them you rub the edges down, cover everything else and shoot paint...
In the case of the masks in the post above the stars would be positioned and the long straight lines that make up the starburst would be made with the aforementioned fine line tape. Then mask and shoot.
I've never personally seen a template used that left a clean, sharp paint edge. On old warbirds the painted-with-a-template fuzzy edge is accurate for some markings.
Vinyl decals have come a long way in the past decade or so, in 2008 we "wrapped" a car instead of painting it and it lasted maybe a year before it deteriorated badly. Today everything from skateboards to beer trucks are wrapped and they seem to last a long time.

Homemade template positioned on the wing.

After marking the outline with a pencil apply fine line tape to make a sharp edge. The 1" Green masking tape over the fine line tape makes attaching the masking to the outline easier...

Cover everything you don't want painted and shoot!
My painting templates were easy compared to positioning multiple stars on each panel so unless you're VERY talented * a pre made mask might make things easier in the long run.
* I myself am not that talented. My artistic endeavors ended at 4 years old when my big box of crayons melted in the sun...
Chris