Faster tires than Primo Comets?
 

I need to replace the Primo Comet 20x1.5 tires that came on my Rans Rocket, after many faithful miles

Any experienced suggestions for a fast 406/20 inch tire for a Short Wheelbase Recumbent?

Well, how about Primo Comet 20x1.35's? A bit lighter and skinnier.

Schwalbe Stelvios are probably the fastest tire you can get for a 406 rim, followed closely by Conti Grand Prix. I have had terrible luck with both, though. Stelvios typically separate the fabric in the casing, causing an S-shaped contact strip. Contis, on the other hand, have very fragile sidewalls - as they wear they seem to sprout more and more broken cords out of the sidewalls until finally you don't dare inflate them anymore. Bottom line, I consider either of them only suitable for racing.

The jury is still out on Conti Sport Contact, which is 28x406 (labelled, as Conti does, incorrectly as 20x1 1/8.) The only one I've gone through suffered premature sidewall failure from what looked like a brake pad cut - except that I don't have rim brakes. And I haven't decided yet if they're faster or slower than Comets.

Primo 20x1.35 is light and relatively fast; but if you get the Kevlar version, expect that feature to cost you some speed.

Be sure to check out the Schwalbe Marathon series tires, there are some fast models there, too!

Don't mess with Comets if you want speed. I dumped my Comet 20 x 1.35's while they were still practically new. If you mount a set of 1 1/8" Stelvios, you will notice a substantial improvement, particularly since you're running 1.5" now.