Captain Juls, this may be a trade secret - and I respect that - but you're so generous with info I thought I'd ask...
Would you share screen shots from your Garmin showing what these tell-tale signs of perch look like? And do you like the Garmin better than the Humminbird you used to run? On my Humminbird, I don't really see anything even when I do catch some. I would love to waste less time on unproductive spots.