Re: Fast 6 wt or slower 7 wt?
You bought a special rod for a special purpose and discovered it doesn't cast as accurate as other rods probably made for accurate casting. You wanted a streamer rod and went to a Very Fast action that should be a dandy streamer rod. If you decide accuracy is more important than bucking wind then the TCX may not be the best rod for you. You might want to consider a Sage Z-Axis. I would cast one and if it doesn't measure up I think you need to drop back to a medium to fast action rod.
It has been my experience that streamer fishing is not an accuracy game like dry fly fishing is. I have never been a really accurate caster but still catch my share of fish. I have never thought of a steamer rod in terms of accuracy.