There should be 6 ridges before they reach the "end" of the chest plate and hang off in the back, so it looks like you're holding them down far enough.
You need to do a couple of things that I can tell...
move them over so they're more angled and pointing inward on the chest
cut them down a bit closer so the "edge" isn't as wide
clamp the hell out of them and glue them down
Here are mine for reference...
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But do NOT use "ME" as reference...
Go look at screen grabs and such to see how much to cut off, how much to angle, and so on.
I think the main thing you're doing wrong is the angle.