I don't think there is any way to do it. L, U and T are considered 'Deeply Discounted'. H, K, and Q are considered 'Discounted'. So for whichever category you choose, it will offer you the lowest fare class in that category. If there is a 'T' available, you're SOL. I have a weekly trip I'm about to start where I want 'Deeply Discounted' for 3 of the legs and 'Discounted' for 1 of the legs for upgrade purposes. I had to call (I hate calling!) to get the fare quoted. You'll probably have to do the same and ask for a non-'T' fare.

The above is my understanding from using the system weekly for a number of years. If there is a way to do what you're asking, I'd love to hear it. Personally, I wish we could search for a given fare class (or higher) for each separate leg of the trip.