We thought about switching to lighter weight tanks, I have bum shoulder and getting two tanks up into the very tight hatch on the Bigfoot 1500 is a pain.
What we found locally (we live in a port town, so lots of marine supply houses.)
A number of places around us sell the composite tanks but they are pricey, close in price to the aluminum tanks.
Around $200 for an 11# tank for the fiberglass and $260 for 20# aluminum tanks.
Viking and Trident are a couple of the companies making the fiberglass tanks.
There was a problem with one type of fiberglass tank, and they were recalled and now lots of places will not refill a fiberglass tank, (even though they are, I know Viking has a special form and they tell you to tell the gas station to call the DOT to confirm that it’s safe to fill the tank.)
The other issue, they need to be re-qualified every 5 years, vs I think 11 or 14 for other tanks, so that’s something else to think about.
The good news a 17# tank weighs only ten pounds.
The cost, the hassle and the re-qualifing are the reasons why we didn’t move forward with getting lighter weight tanks.