Oh jeez, you know, I posted a picture of a tool I made 15 or so years ago.... Ha! About a curved square foot of virgin corrugated board with 1/2" roofing nails on a 1" grid.
I could look for it, but the end is, I poke little holes all over the deck/rails/fin area for the glue to anchor in. Hence, "post holes..." Ha!
I think the vent/drain holes is a helpful tact too - I got a slight bubble on a pronounced convex curve on the deck side, where the belly ends at the rail/tail juncture - takes a lot of pressure - and it was pretty minimal. The posts kept it down and vent holes kept it from spreading.