You can use spa flex or sch 40 pvc. Both have pro's and con's. One is cost, and the other is time consuming. I use a ton of both, and it depends on the situation. I like the rigid sch 40 PVC for closed systems. I think you need to just take your time, and use fresh primer and glue, make your cuts on a chop saw, de-burr everything, measure 2 times and cut once and get after it!
You really need to design it to be able to do maintaince on it. At the bulkhead use a true union ball valve, and buy good ones. They are not cheap, but neither is having your tank on the floor! I have had customers take my reccomendations, and spend 1500.00 on plumbing all the time. Do it right and cry once.
Just my .02.
If I can help in any way, PM me, Jason