Sometimes the right answer isn't the one you're looking for, O.P.!
You ask if anyone's ever built their own gas tank.
Pretty much, everybody's checking in saying
"Why would I do that, when there are so many other existing practical alternatives"?
If you'd rather do it yourself, you just go right ahead and do it!
Just don't expect anybody to tell you it's the smartest/most practical/cheapest/safest alternative to your extra fuel-carrying problem...
Bingo, we have a winner. I think that is all people have tried to say with "constructive" criticism or alternative suggestions. IMHO there is way too much knee jerk "approval" of various questions raised in this forum.
since we are straying off topic, if you make your own gas tank, ever have a wreck where it bursts and a fire ensues, get out your check book.
Man speaking of off topic!! Did you see that explosion at Daytona 500 I wonder if that was a legal container he had fuel in?
Sorry you haven't found the answer you're looking for...yet.
Not claiming to be an expert on NASCAR requirements, since I feel NASCAR racing is really designed to appeal to folks who can't grasp the subtle nuances of professional wrestling, I would "guess" that gas tank specifications for cars and other equipment is highly regulated.
You can build one in a heart beat. Figure out where you want all the connections, add baffles, I would recommend testing it to 6psi and use a 4psi releving cap in case the vent ever stops up. Soap and water works great on for finding the leak if it has one, alot cheaper than dye check and alot cleaner.
The davantages to building your own are you can make better use of the space you have. (get a larger tank than a straight up 20 or 30 gal) Just keep in mind what needs to support the tanks weight. The empty weight of the tank, the weight of the fuel capacity, and I would add a 30% weight margin in for slosh if its not completely full.
So if your total is 400 lbs, add 30% to it (520 lbs) and that is what the supporting structure needs to be able to handle.
2008 Ford F350 CC LWB Dually
2011 Raptor 4014LEV
2006 H-D FLHX
2010 Honda Rancher 420ES
I made one for my old one lunger Fairbanks engine, it was about 2 gallons. I had a metal supplier cut and bend 2 sheets of lightweight metal then I simply welded them together and added flat stock across the bottom to attatch it. I used the correct size pipe fittings for the fuel line and filler.
2005 Dodge 2500 4X4 Cummins, BD Exhaust Brake, Edge Juice W/ Attitude, Banks Technicooler.
2009 Enduramax G-Force 3105 Toy Hauler
2012 Polaris RZR XP 4 900
2006 Kawasaki KFX400
Did I miss something at the Daytona race I was unaware any explosion happened. I did see a fuel oil fire, no explosion.
If you are a proficientnt welder have some metal cut and bent to your needs. Making your own custom tank that fits your application has its advantages. PRESSURE TEST TO 6 lb. I would however, first shop for something off the shelf that suits your needs, probably cheaper and less of a pain.