Rick, I bounced around with this on the net and the way back machine this morning. Most PVC pipe are ink jet printed I believe during the manufacturing...although they may use a roller method too because it's repetitive lettering.
The main etchant/solvent in the Oatey stuff is Tetrahydrofuran, but I think the bleed problem you are having is from the Acetone in it. Here is the MSDS of the Oatey stuff.
Most PVC is screen printed nowadays with ink but its way pricey. I used industrial ink jets on my DM's and was amazed by what that stuff sticks to and through coolant and UV/heat resistantant...again Pricey. Here is an ink I found.
There was a Mastic product I used years ago air brushing bike tanks...came in a bottle you could brush on any area, shape or size, and they had 8.5 x 11 sheets too...kind of like a sticky backs but can't remember the name of it or find it on the web. I got it at a local art supply store, and as I remember at an auto paint supply too. I know it's still out there because it was goooood stuff and worked with all kinds of paints and thinners....including acetone.
Then I got to thinking about Cell phone screen protectors...the old ones were adhesive and can get them pretty cheap. Maybe a Galaxy note size. One off though and cost will accumulate.
The sticky back Idea would mean cutting out a place for your vinyl stencils (which seem to work Pretty Good) but it wouldn't have the corner/edge bleed problem and if you can get it in rolls or sheet you can make multiples...which begs the questions. Can you find blank sheets of the vinyl stencil material?
All the same size pipe?
A good challenge Rick, Thanks. ~PJ