Re: Choosing fly line -- Redington CT 9' 4wt
You are correct about the half heavies. Stay away from those.
If I was going to choose a line based off of past experiences with that rod, I would look at the Scientific Anglers Mastery Trout and the Wulff Triangle Taper lines. Both are great general purpose trout lines that have good dry fly presentations.
There are some dry fly specific fly lines that have long front tapers. I have not cast them on that rod.