This may be out of your geographical area, but I'm sure if you called Steeves Agencies at (204) 474-1239 or by emailing
brian@steeves.ca , and asked for Brian and let him know I sent you he'd get you some real heavy duty rails - for you - and whatever else you were looking for. I've been in the warehouse and lots of ideas have come to mind when seeing what there was to offer!
I once considered putting a tank on these rails, but decided not to at last minute. Great selection of stainless steel hinges as well.