Not sure of the worth of street Aldans for 'vigorous' driving. They have an external damping screw that is often the leak source. Hall used to get one or two a week back for leak fixes when he was selling them. He once described the fix:
* Remove the shock and rotate it upside down, then unscrew the damping adjuster until it comes completely out of the shock body. There is a tiny o-ring on the end.
* Replace o-ring (maybe with a higher quality), lube it and reassemble. If you try doing this without tipping the shock upside down, all the remaining fluid inside (if any) will run out.
Old time motorcycle shops sell shock oil in various viscosities. Not sure how much oil or what weight should be inside; that's why Gary was in business! Too much will likely blow the shaft seal out on a big bump. I think Aldan was sold at least once since the good ol' days.