Fly lines wts are a very foggy business. Some lines like the cortland 444 and H&H lines fall within AFFTA line wt standards, others exceed the AFFTA line standard by a half or more. Furthermore if a caster carries a lot of line in the air when casting the grain wt of the total head length might be 1-3 line wts higher than what the line is rated by the manufacturer. A 5wt line might actually be a 7wt line when 45 ft of line is beyond the rod tip. This is especially true with double taper lines because the have no running line.
If you really want to get geeky about the line wt stuff Umpqua sells a line wt scale for around $20. It can be a real eye opener when comparing line wts. from different manufacturers.
So if you like a 4wt rod with a 5wt line then by all means use the 5wt line. Line wt designations vary so wildly from manufacturer to manufacturer that there really is no industry standard anymore.
Another vote for the H&H high floater. Great line!!!
I don't have any idea what the many lines I have are. I know a couple are Cortland 444s but beyond that, its anybody's guess. All I know for sure is their weights according to the manufacturers. Not being acute about lines has never seemed to hinder me except for the raillery from my companions about a couple of bottom end Cabela's lines that are an obnoxious orangy red and an ancient old Orvis line that is pink. (Those lines work just fine.)
In short, don't get torqued over lines. Other than weight and configuration its mostly hype.
As to overlining, if I need to fish close in, I find using aan 8 wt on a 3 wt rod keeps the casts short.
I really like the Aqua Nova 99 lines from globel dorbeR (also an FAOL sponsor). I have a WF5F from them and a WF5F from Cortland and have used both for about a year now. The only difference I notice is that the globel dorbeR line is $14.80 and the Cortland is $52.
JW