Scratch should be used as a treat for the most part. You can mix the two and it will not hurt, but keep in mind the corn in scratch from what I understand raises the chickens body tempature. You may want to be careful doing that in Florida.
I did that when I first got my chickens b/c I didn't know better. Since I only have 5 adults it's taking a while to go through it, but they tend to throw a lot of the feed out of the feeder so they can get to all the scratch and are wasting a lot of it.
I can't wait until this batch is done and then I won't do it again!