Sorry this is not going to help a lot unless you end up going the same way.
I looked into bladders for range insurance for an occasional offshore albacore trip. I finally ended up purchasing four 6 gal. poly tanks after considering my number of probable uses vs. cost. Easier to fill and move around, snap on outboard hoses, can put the operational tank in the motor well. I use these auxiliaries first and then store the very light and non scratching empties on the roof/bimini under a pre-stretched truck bed bungee web. That way at least 2 or 3 are usually pretty much used up and out of the way prior to fishing.
I often take 1 poly with me, even a shorter trips. I frequently run the kicker or generator off it. I find it rides well in the splash well and provides me with options if there ever were a fuel delivery problem with the main tanks. I also once sold one to another boater with fuel problems. Though I didn't make anything off it, not having to tow the guy back in was payoff enough for me.