I started out with the heavier grand on my z-axis thinking I would need it for the fast reputation of the rod and my poor abilities but the Gold was the answer for me in the end.
I fish a SA Textured GPX taper on it when nymphing and streamer fishing (4 & 5 weights) and I feel it is not as heavy as the grand, but certainly more so than the Gold. I should try the Gold on mine, I've not actually done that. Now for dry fly fishing, the SA Textured Trout Stalker is an amazing line on that stick. Wow.
It's been my experience with a 9' 5wt Z-Axis that the rod does not like to be pushed or rushed. My casting stroke is very compact with the Z-Axis, something I developed after finding the rod very frustrating at first. You've been using much softer rods (I only take out my ZXL once in a while now), and they could have effected your timing. I tie my leaders, and find they turn over much better than the store-bought extruded types. Even my 6X leaders begin with a #50 butt section.
Though Gold is the gold standard for modern Sage trout rods, SA TroutStalker and Expert Distance Taper (for those who prefer a quite line) are excellent too. Grande, which I have tried on both Z-Axis and ONE is clunky and overweighed for these rods but, after I rejected it, found a perfect home for it on my friend's TFO BVK #5 where it is just the ticket. GPX has a very short rear taper behind its half heavy head and is fine for non-dry fly power tossing I imagine but just will not promote loop stability at distance where it is prone to hinge and loose accuracy and mending acumen. I have been won over by ONE, as I have said before, but remain of the opinion that softer tipped Z-Axis is a brilliant rod with added flexibility for in close presentations. As Frank said above, it is crucial to build leaders that turn over effectively, controllably and promote optimal transfer of energy from line tip to leader butt.
For what it's worth SA sent me a new spool of mastery GPX to replac the one I sent in for them to review. They did not give any feedback as to if the line I had was off spec or not. I hopefully can get out within a few weeks to try it out.
Kudo's to SA for good customer service, I wasn't expecting a free spool but I certainly won't complain.
Interestingly enough I had issues with my SA GPX line, the material along the rear taper has small cracks throughout the length of the rear taper. The cracks are such that if I bend the line at one of the cracks it opens and I can see the core. Pretty bummed about this given that I've only had the line for a year.
However, I went ahead and sent the line to SA warranty dept. and they have agreed to take a look at the line and decide if its a manufacturer defect. I'm hoping they will sen me a new line.
Has anyone here had SA send them a new line after sending in a damaged one??