You will see less loss with heavier bullets in a shorter barrel from what I've seen. My 7stw has a 10" twist 24" barrel and she'll do the 3,000 fps mark with 175's without issue, but tops a bit low with 140 grain bullets; Still in the 3200-3300 fps range though. If you look at most stw book data, it is in 24" bbl.'s. Speer even says in print they haven't seen much difference between 24" and 26" stw barrels. Powder choice is more important that those two inches of barrel.You definitely can, just depends on how hard you push your handloads.
My question is, who would order a 24" barrel on an STW in the first place? I think all centerfires should have a 26" barrel, except the .308 Win and .300 BLK. Those can get away with shorter barrels.