If you're using a hopper pattern or other bigger dry fly, a 6x leader won't straighten out on the cast. There's nothing magic about 6x for the dropper either. It will sink faster and help with drag, but you'll lose more flies.
5x usually. I almost never go down to 6x unless I'm fishing tiny flies in low water. I don't think it makes any difference, except you don't break half your fish off setting the hook. I have a spool of 6x that has lasted me many years and still half full. 4x -5x is my go-to tippet for most things, 3x sometimes for nymphs and streamers.
4x and 5x 95 percent of the time. I had a young girl about 11 years old couple weeks ago that keep braking off on big fish in our private water. I ended up cutting back on the leader until it was around 15 lb test and with a monster streamer. She ended up catching more fish than her mother or father who were using 4x tippet. Match the tippet to the fly being used is best in my book. I seldom use flies that require tippet smaller than 5x.
Really was trying to get a better cast with a 4wt Scott and hopper dropper
set up. I thought maybe further tapering the 5x down to a 6x dropper
would help. Really doesn't seem to help. I usually just get a non-
extended 6x fly. I think I am going to switch from the SA trout 4wt line
to a a different line. It throws a 3wt perception line better for me with
a single fly. I may try Rio Gold. Just not happy with my hopper dropper
cast and the GS 843. Im sure its my cast with the hopper dropper setup
and not the rod.
Hopper I’ll usually use a 4x leader and tippet with a 10-14 hopper. I’ll then use a 5 or 6x for the dropper fly depending on fly size.
Leader length depends on which rod I’m using but majority of time I use a nine foot. I’ll use a 7’ leader on a 8’ rod set up as it performs better with that length compared to a 9’ leader.
No pro caster myself but the added length of tippet on a dropper rig causes some consternation for me if my tag end fly is to heavy or the tag is too long.