Rolf,
I have also heared (and I sail like this) that you better have the windward tell tales at 45° when you're trapping out. Otherwise I sail them flowing for more pressure.
Concerning the main, I only look at the tell tales at the luff (back) of the sail at the top 3 battens. Do you guys look to the entire mainsail? (I don't think I have time to look at them all :-) )
Gill