When I installed my seat I over drilled and filled with thickened resin and then drilled and inserted thesehttps://www.zoro.com/e-z-lok-thread-insert-ss-10-24x1332-l-pk5-303-3/i/G1292785/feature-product?gclid=EAIaIQobChMIwtbEo7Tb5gIVc4NaBR26cgnqEAQYAiABEgL22vD_BwE
Also - will a typical cooler fit between the tubes on that leaning post? I think you would want that...
Highly unlikely the leaning post flanges will be inside the width of the 2 stringers, which means you won’t have access to use thru bolts. Though thru bolts is always choice for permanence, it’s not a necessity here...like the need to secure a tower, for example. Get an accurate measurement of the deck depth and subtract 1/4”. That’s your screw length. Get the widest screws the flanges will allow for the greatest screw/wood purchase (aka grip). Under drill deck holes. Dip screw threads in 5200. Drill gun halfway at most. Screw in by hand to finish. Don’t fill the pre drilled holes w/5200...screw will push out excess which will cause the underside of flange to bond w/deck.
Argh. Leaning post mount are going to be very very close to the fuel tank coffin to deck seam. Makes it tricky. DMay not be able to mount dead center. Landed on a Dolphin brand leaning post with backrest and rod holders