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I assume this is a 2012 or newer Montauk 210. Are you thinking of modifying you RPS (reversible pilot seat) so it can't be reversed any longer as you'll have a tackle-box hanging of the seat back??
Can you post a sketch of what you are planning?
I don't think the owners resources gives you a schematic of the seat except maybe the final assembly drawing showing the RPS.
A sketch will help and as mentioned before starboard as no real structural strength as compared to solid wood or even better marine plywood.
When seriously fishing I just bring my 4 drawer Plano with carrying handle on board. Problem solved.