Save your self some grief get new made up (you have gone to alot of work to put used **** in) and go with belly tanks as it makes a boat way more stable FYI and put it mid ship in between the stringers...
Your 26 should have plenty of room for an 80 gallon tank between the stringers and go plastic as "SteelyDan" says. If "We're" going to build "Your" boat ,lets do it right.
Especially with that command bridge up top you want as much weight in the belly as you can .... think of a sailboat the have them full of lead for a reason in the keel..
how many gallons is it? if you need more put another one in there if it more then 50 gallons thats PLENTY of fuel , unless your going offshore for tuna then all you need to do is bring some jerry cans
80 gallons is a lot do you plan on going somewhere with huge distances?
50-75 miles seems adequate. Even for tuna. Lots left for the return trip with safety in mind.I only say that cause you start adding more and more "weight" it will definalty effect the way the boat handles etc I would opt to putting in another tank in the belly then. (tempo) or opt to getting a HUGE tank built.... and lay the sucker on the bottom of the boat you have lots of space and time to do it, as if you have 2 side tanks that 2 extra filters, hoses, valves, connections etc....so thats 3 filters every year etc
I have a 26 hourston and it has a 80 gallon tank and im never really low on fuel my boat is very heavy being the model it is and the new motor runs at 10 gallons a hour at 25 mph I dont run it hard. thats the "sweet" spot on it.
Why not a Moeller poly tank? Lots of options....I like the idea of one big tank. I get wanting the option for lots of fuel. I’m putting a Moeller 60 gal in my 20’ Grady. Much smaller/lighter boat than a hourston 26’