look up at the top right hand corner of this forum
and you will see a box that says "search" - - - -
type in "deck framing".
many good build threads can be found there.
you might get lucky and find a boat just like yours to get ideas from.
for example, try this link: https://forum.tinboats.net/viewtopic.php?f=21&t=41155&p=423252&hilit=aluminum+framing#p423252