Making your own additional fuel tank?
 

Has anyone here had any experience of manufacturing their own fuel tank?

My GS Dakar has got a Staintune exhaust which means I've got a nice little gap where I could probably fit upto another 10 litres of fuel if needed.

How easy would it be to make or adapt something to fit that would be safe for carrying fuel?

options
 

I know of a fabrication company that makes fuel tanks for stock cars etc and its basically just a welded tank. If you were travelling somewhere hot you'd probably want it to have some kind of a blow out valve but that shouldn't be too difficult. When they are going into bangers for contact racing, builders often use modified fire extinguishers as they are very resistant to piercing.

None of these solutions would be certified though and would require some quality workmanship. If you wanted an easier solution why not make a rack that will hold a 5l or 6l jerry can. I have seen some steel ones as well as the typical plastic and they seem to come in various sizes and shapes.

They would be road legal then if that's and issue and would have been checked for thermal expansion.