My 37 tank was in pretty bad shape. I bought the POR kit back in 1999 for about $50 back then. I did buy some muriatic acid from Lowes and spent one afternoon cleaning, and then coating it inside. 8 years later it is still nice inside. I can look stright down into it as its directly under the seat of the 37 and its holding up good. I might add that with the kit came enough of the regular Por15 to coat the outside as well.
This is just MY experience.
Yes, I want to put the tank under the bed but haven't found the right solution yet......meaning some way that doen't rob the bank