If, after the arbitration meeting (T2) the arbitrator's opinion is that a boat or boats is likely to have broken a rule [T3(c)], may a boat decline all of the meeting outcomes [T4] and request a hearing or does she need to accept T4(a) and then file an appeal?
“Unless all protests involving the incident are withdrawn, a protest hearing will be held.”
"Unless all protests involving the incident are withdrawn, a protest hearing will be held."
If a boat declines to take the penalty recommended, it goes to a full hearing. If the boat takes the penalty, but the protestor doesn't withdraw, it goes to a hearing. Now, if the protestor doesn't want the lesser penalty, you can point out that a permitted outcome is that the arbitration penalty was an appropriate penalty and you cannot "force" a DSQ because you don't like it, most of these will be withdrawn.
Of course, if things are on the border of damage or serious damage, the full committee could determine it was serious damage and the post-race penalty does not apply.
You may always refuse the arbitrators decision and ask for a hearing.
Indeed you can accept a post race penalty, and still ask for a hearing
That's not the correct way for an arbitrator to express their opinion. The Arbitrators opinion can be:
'[Based on what you have tole me] A protest committee hearing the protest is likely to:
In my experience, when the opinion is other than to penalise a boat, it is still useful to ask the parties if either party wants to take a PRP, and (except in the case of serious damage or sportsmanship concerns) ask the protestor if they want to withdraw the protest. Having heard the other party's description of the incident a party may re-assess the strength of their case and make that decision.