I never said "stay smaller" I said "relatively small". Central stonerollers do not get up to 10", ever. They have an absolute max of about 8.5" but rarely get over 6". Also you'll notice if you actually read the OP's posts he says he is upgrading from the 20 gallon. Quit acting like you know more than everyone.
Central stonerollers do get up to 10". How I know? I sampled them during my internship with the Fisheries. They do get bigger than 6" and it's not uncommon. Perhaps I wouldn't be a prick if someone is so misinformed and suggest a wrong species for a wrong setting. Just because the OP is upgrading from the 20gal, doesn't mean he is getting rid of 20gal or planning to add more fish in the bigger tank for the crappie and the warmouth.