As a holding tank
you can't ventilate it, so it may create an odor
When good tanks
are installed carefully--so they won't chafe on rough spots in the fiberglass
, etc., and you use an anti-chafe or padding material around them to make sure they won't chafe, and you secure them so they won't be sloshing around...Seems like the folks who treat them carefully get good life out of them.
I'd still use a fixed tank IF the space was going to be dedicated and available, but as a way to carry extra tankage when you need it, and make the space available when you don't, they're a great idea.
The military also drops thousands of gallons of fuel
in flex tanks--better known as "blivets". If they can trust 'em with fuel
, you can probably trust the small ones with water or waste.<G>