Spray Glue or Liquid Glue?

In preparation for doing the bellows cloth stiffeners, I wondered whether it would be better to use spray adhesive rather than the liquid wood glue that I'd been using for all of the wood parts.

The idea of a loose stiffener rattling around in the bellows years down the road didn't really excite me, and while I suspect that the liquid glue is superior in gluing wood pieces together, I wondered whether the spray adhesive might be less brittle and apt to work itself loose over time on something flexible like the bellows cloth.

Of course if the spray glue would be a stronger choice, then it would also speed up time in the gluing of the bellows stiffeners by cutting down on curing and clamping time significantly.

So, I decided to conduct a little experiment.

First I took a scrap of bellows cloth/blackout fabric and glued 2 pieces of cardboard stiffener scrap to it - One with the Titebond liquid glue, and one with the 3M #45 spray adhesive.

Then I clamped it between two boards and let it dry for 24hrs:

I put the test strip on a torture device that would cause the fabric to bend and stretch under each of the test cards:

After 20 minutes, the spray glue side showed no real signs of loosening:

While the liquid glue appeared to be letting loose slightly at the corners:

After an hour, the story had changed.
Here's the spray glue:

Here's the liquid glue:

So it looks like I'll be sticking (haha) with the original scheme of using plain old liquid glue. At least now I won't wonder if it was the best choice....