hi YM
start line timing : not really useful for upwind starts (imo), much more for reaching start as in F50 or nacra ... it gives a timing at your current speed then it changes if you are faster / slower or if an opponent put a shadow on / cover you
laylines help to not go out of the course ... always better to have a shorter distance
best vmg is clearly mandatory ... your boat will perfectly follow the shifts and it gives you time to manage your tactic and the fleet
wind shadow is helpful when you begin ... then you should know the shadow ... even if you DON'T pay for it, you have an effective shadow ... it's only visibility
wind intelligence : you must take it ... the socks of you boat is the wind you have right now ... the socks of the little radar in the left corner is the future wind ... if you are at the bottom of the course, you will have it in 20 to 30 seconds ... at mid course, count 10 to 20 seconds ... at top edge, you will touch this windshift in a few seconds
i do always use (in order of importance) vmg, wind intelligence, laylines & start timing for F50
hope that's clear enough, cheers lmn