I used a 5wt GPX for over 4 years with the Z-Axis 590, and it was my go-to non-dry fly rod for all that time. I argued with people on this forum who said the Z-Axis needed a 6wt line to lad properly, and reported that mine worked with a 4wt GPX. A former poster (and self-proclaimed expert) said that the Z-Axis was incapable of roll casting at any distance. I made a video and posted it here, of me roll casting the Z-Axis with about 10 feet of line out. I hit the target every time, and was using a weighted nymph.
Pennsylvania has been a non-stop wind storm all year. Jim Landis tried to get me to at least try a 6wt line with the 590 Z, and I resisted for the longest time. We had temps in the 70's and 80's during the first week of April, and the big smallmouth came to dinner HUNGRY! I consider myself an above average caster, but casting Clousers into howling winds finally convinced me to try the 6wt line. While a heavier rod would have worked well, a shoulder injury makes using 4-5wt rods a must. The first cast into howling wind almost made me howler with joy! Delicate presentation was not a concern, and was not happening: it just blasted the Clousers right on target every time. After a couple months of using the 6wt line, I can deliver a dry fly with acceptable
results...i.e. I catch fish.
The wind wasn't quite so strong a few days ago, and I almost strung the rod with a 5wt, but decided to use a 6wt. Good thing, as the wind picked up to the usual gale force once I was downstream a 1/2 mile. I did carry a 5wt spool a couple times this Spring, but haven't seen the reason for using it.
I read all of your posts, and respect what you have to say. I'm not trying to argue with you, but I've been fly fishing for 35+ years, and this combo feels great to me....and Jim Landis.