Re: How do y'all cast your...
I'm not really sure why it would change so much when removing the indie.
The fly cast is a funny thing. Fishing my 490 SLT yesterday with small indie and two small nymphs was giving me fits, when I moved to a small streamer (still with indie) the cast was smooth as silk. Moved back to the nymph set up and I was casting great. What changed? My stroke I suppose.
If I was to provide judgement without witnessing I would say it is possible that when you were fishing with the indie you were tossing relatively open loops. When removing the indie and still fishing the nymph you may not have tightened up the loop and kept it as open as when fishing the indie tandem rig, thus causing your problem.
As an aside, my main trout rod in the Midwest is an 8.5 Sage ZXL, I fish tandem flies, indie rigs all the time. Flies 14-20 with Dinsmore shot up to BB in some instances - small float. I open it up when throwing the rig that way... and tighten it up if I switch to single fly/dry dropper. Hence my commentary.