Leaving it the way it is makes sense, mostly because if you like the swing adding chokes may change that for you.
There's no reason you can't shoot SC with Sk/IC, depending on how good you are at far and rising shots you may miss some more than with tighter chokes. I've seen shooters with automatics and a LM or Mod take more birds than I ever could, close, far, crossers, rising made no difference.
Rocketman has made points above that sound like they were well earned, and I agree with them all with possible the exception of #1, I don't know a serious skeet shooter that uses a DT SxS so your 26" tubes are just fine. I shot my first perfect round with a Browning BPS with 32" tubes and IC :-)
Casual shooters like you and I can and do shoot anything and everything they like including pumps, SxS, DT's and automatics while serious skeet shooters AFAIK use O/U's and tubes tailored to skeet.
Some like me still value skeet as a fun game that can give the casual shooter a leg up on open season in the field.
