Tannoy Owners: Need help with Canterbury GR fine tuning.

I recently got a pair of Canterbury GRs which have multiple adjustment on treble level and treble roll off.  I prefer the tonal balance with -2db roll off and flat treble energy setting.   The sound is more focused and balance.   The soundstage is more focused but slightly smaller.   With the treble roll off set to flat, the soundstage is wider and taller ( imaging outside of speakers ).   The very high notes of the piano deem to have longer decay ( which I like) However, there is exaggerated sibilance of human voices and a overall a little bright.   The degree of changes are somewhat cable dependent but the same trend is observed consistently observed across different cables.   

I have played with speaker positioning and toe in.   

What do you guys use for your settings and how much toe-in?

Does biwire make a big difference?

Thank you