If you are looking to do a decorative carpet on the stairs (only) then one way to do it is to use the carpet as a RUNNER...not a stringer-stringer carpeting. The other thing to consider is normally the stairs should match "something". If you have different carpet at the top of the stairs that does not match the stair carpet, that NORMALLY means you have different carpet DOWN stairs. The stairs will match the carpeting on the MAIN floor. I'm not hearing that this is your scenario. What type of flooring do you have on the main floor? This is what the stairs will be MATCHING if you choose to go this route (stairs not matching carpet upstairs). The other way to do this is to use the decorative carpet on the stairs and then pay to have an area rug cut and bound in your chosen "stair" carpet. This area rug then sits in the entrance/bottom of the stairs. This is a quick, easy (slightly less expensive) way to get the stairs to match "something".....'cause they really should match something. Right now they match the upstairs carpet. Once you change this design feature, you need to REPLACE it with another version of "must match something". The bound area rug in the same carpet is one of the fastest ways to do this. Good luck. Remember to look at your main level flooring and decide whether or not you want to go forward with this concept.

This is exactly what I’m worried about. What did you end up doing?

Taking everything you say at face value,turn dowstair unit off.

Definitely match stairs to your main floor. When I'm on my main floor, my basement stairs are quite visible. It would drive me crazy if they didn't match the surroundings (FWIW, once you get downstairs there's a laminate floor that barely matches, and I don't really care because the basement is a casual space).