Dodge had a answer to this problem back in 1997, they made replacement side rails. Talked with the guys from Dodge @ the Orlando VOI
Had mine covered under warranty. It had a bigger arc to compensate the saggging side rail, cause was from the sun it got to hot and it sagged. The top was very loose when the rails sagged
I think the replacement cost was about a $800.00.
It also has a different locking mechanism for the rail, it no longer uses the slide lock, now it uses an easy screw,
They drilled a hole in the rail and use the existing stud thread, the stud was removed with a screw driver that was used from the slide lock.
When you put the side curtains on, the top of the curtain has a gap because of the new side rails, there was an answer to that buy mopars side curtains, they were adjustable, bulb weather stripping and seem to fit better. More $$$$$$
What I can say after all this is you still can't keep water out!!!!!!
The joy of having a Viper! (95 RT)
Haven't had a problem since with sagging side rails.
I'm sure you can still get these.
Part #5010323AA this is the only number I have from the write-up @ the dealer.
They came as a set.
Good luck
Sam