Good times, great oldies.
Definitely worth the trip above 850, and 1500 or higher is fantastic. Above 1000 you can head down to the Ledges section, which is a 1/2 mile below the Salt Cliffs (where the road to the Flat bears away from the river). The trick is that the river right side- where the road is- is sacred land, and ****** mush not walk upon lest he recieve a hefty fine. You'll have to bushwack up the river left, then ferry back across to your car. But, it is one ledge hole after another for about 100 yards (kind of like that one section near Stoner on the Delores). There's also a pretty nice park-n-play hole at the mouth of Cibeque Creek. The whole run is a great time, and the water will be significantly warmer than anything you'll find in Colorado during March or April.
However, the day permits were $15 per boater from the Apache tribe last time I was down there, and if you sneak on & they catch you they will take your gear and fine you heavily. Also- as amazing of a big water V run the Upper-Upper Salt looks from the road, it is also sacred land and they will arrest you if you take a shot at that one.