Workshop in Progress

This is my first time joining in the Workshop in Progress.  I'm excited by the chance to get feedback from a wider group of people.

I am working on my prep for my wedding signature quilt blocks.  There are two issues that I keep coming back to.

The first is making sure that guests sign on the right part of the block, inside the seam allowance.  What I've come up with so far is adding a freezer paper backing on the part that should be signed.  When I made a mock-up, I realized that I could write on the back of the freezer paper to explain.

Back side

Front side

The question is - does this make enough sense?  Eric suggested I add a border to the back of the freezer paper in dark Sharpie to make a clearer frame.

The second question is pens - I've narrowed it down to a Sharpie or a Pigma pen.  I've tested both and found that the Pigma pen bled a little bit but had a bolder result.  The Sharpie looks faded but doesn't bleed.  Any advice or thoughts from people who have done this large-scale?