Hi Steve,
I'm surprised someone more knowledgeable than me hasn't answered you yet so I'll give you my 2 cents. Bottom line is, use what works. If you know someone who has already built the ship your going to build, what did they use and was it sucessful ?. I built a profile with an ST46 on it and I mounted every metal tank I had in stock on it (about 4) and none of them worked (runaway, runaway) to my satisfaction. So I tried a Sullivan plastic with a clunk, bingo it worked great. I'm not saying to use a Sullivan, Just keep an open mind and you may have to experiment like I did until you find the right combo. I have used metal tanks in other ships that worked just fine. There is not always a pat answer to your question so when you build the engine crutch keep in mind what tanks you might like to try if the first one doesn't work. Also consider giving Randy Smith a call he is really familiar with your problem and can probably make a good suggestion right off for the PA 65, saving you having to go thru a bunch of different tanks. Good question.