I hate to be the bearer of bad news, but there are no modern folding bikes that are officially rated for your weight requirements. Have you considered an S&S coupled bike? It's not exactly a folder, but you can still stow it away after separating it.

You're right that Bike Friday's heavy rider upgrade goes to 260 lbs. If you got this info from their website, you might want to call them directly to see if they can accommodate a higher weight on some specific model.

Another option is to go for something old and heavy... like an R20. Oh... or maybe one of the DiBlasi bikes can handle it, they seem to be built like tanks. One last option to look at is Montague's line of full-sized folders.

--sam