Re: Question- Leader Lengths/ Fly sizes????
On a 5 wt, with your wf line and a 9' 3x leader you should be able to throw unweighted flies up to size 8 without too much difficulty, and get them to lay out properly instead of collapsing in a heap of leader at the end of your flyline. If you can do that as a beginner, you're on the right road.
Heavier flies like a #8 Conehead Woolly Bugger, and wind resistant #8 poppers may give you a little more trouble at first if you are just starting out. Larger flies may be more of a problem, especially if they are heavily weighted or wind resistant. Keep in mind a sparse unweighted #4 like a Mickey Finn or Black Nosed Dace (bucktail streamers) may be easier to cast than a #6 weighted or a wind resistant fly (like Poppers, Dahlberg Divers, EP Minnows, Clousers etc) so consider aerodynamics and weight in addition to hook size when you are shopping. And if you tie, keep them sparse for easier casting and better action in the water.
As your casting stroke improves and you start generating higher line speed, you should be able to throw these better too, and you should be able to sneak up to size 6 with a 9' leader on the right X size tippet for the fly size. (Divide hook size by 3 to get approximate tippet size, for example size 6 hook/3= 2X tippet) Right now it sounds like like maybe the fly line is running out of gas at the end of the forward cast. A bass bug taper can help. But before you buy one try shortening up your leader and see if that helps.
Since you probably want to throw larger flies for bass, 6's for sure and maybe 4's and the occasional 2, as well as weighted flies like Clousers etc., I'd suggest shortening your leader to 7 1/2 feet tapered down to 1x on a floating wf line. Since a tapered leader is supposed to turn over the fly, the lighter the fly, the longer and lighter the leader can be. For heavier and/or bigger flies, a shorter and heavier leader might be the easiest solution on a 5 wt rod. 1X would match up well with size 4 (and even 2) hooks, but since bass are usually not leader shy, you should be able to use 1X on size 6 and 8 stuff too, and it would be a good match with wind resistant 6's like bass poppers and bass bugs, weighted patterns like clousers and crayfish patterns, and heavily weighted # 8 buggers. Ir might also be a good choice around rocks and lily pads anyway. And you can just add 2 ' or so of 3x tippet for panfish stuff on size 10 (and probably 12 hooks) if you do that.
If you are using a 5 wt wf sinking line or sink tip for bass I would just use a straight shot of just 3' or 4' of 12-16lb test mono. No taper, no nuthin'. This will keep your fly down where you want it on a sinker (instead of riding up on a longer leader) and that would make casting larger and/weighted subsurface flies even easier. A sinktip is also a sneaky and very effective way of getting unweighted streamers down to fish instead of using harder to cast weighted flies.
Hope this helps.