Yes, use the 24mm float setting. The '78-'79 carb set pretty much always needs the needles leaned when larger mains are installed. I'd just do it as part of the jet install. Don't do it before you get the larger jets in there. That would make it too lean now. Look at that carb circuit drawing I posted a couple posts up. Your new larger mains and pilots are going to make the midrange too rich because of the circuit overlaps. The usual scenario is you do the mains first because they will effect all the other settings. In your case 2 to 3 sizes up should do. That will probably induce the upper midrange break-up I mentioned. You fix that by leaning the needles a step. Now, the stock pilot is usually fine as long as you haven't leaned the needles. Once you do though, due to the circuit overlap, you lean the upper part of the idle circuit as well and that usually creates a flat spot or hesitation just off idle. The larger pilot is then needed to cure that.