Yeah, that's what I found with Eduard's masks for their P-39 kit.  Even after burnishing the edges with a toothpick, some of the mask still lifted a little.  But the same toothpick served to scrape away paint that crept under the edges, too.  Not too bad.

Golanthius, I had the same thought about what looks like some paint that crept under your masking, too.  You can use a toothpick to scrape it away, back to the raised edges of the canopy panels.

Thanks for your experience with a liquid mask compound, too.  Sounds like it's not worth it to me to try it and change my process.