This pertains to Rule 18 (rounding or passing marks)

Here is the rule:

18.2.e OVERLAP RIGHTS
[color:"red"] If there is reasonable doubt that a boat obtained or broke an overlap in time, it shall be presumed that she did not.[/color] If the outside boat is unable to give room when an overlap begins, rules 18.2(a) and 18.2(b) do not apply.

I'm confused about the highlighted section. One boat may have doubts that she obtained an overlap while another might have doubts that she broke an overlap. It seems like this doesn't really spell out who should do the avoiding if there is doubt about the overlap.

I've always read this as
"if you are claiming an inside overlap, you need to prove it at the protest"
"if you are claiming you broke the overlap, you need to prove it at the protest"

So one boat claims she has overlap, the other boat claims she broke overlap in the same incident. I don't see which boat the burden of proof is on?

If you ask for water, you prove you have the right for it.

If you deny the right to water, you prove you had the right to deny it.

One will have to come first (either the hail "no water" or "water")

So approaching the mark:

Inside boat calls for "water" (and it's a little tight) then you give it and protest them and they then need to prove they had the right to it.

OR

Outside boat calls "no water" (and it's a little tight) then you duck them and protest them for not giving it, they then need to prove that there was no overlap

One thing I've been told by many sailors is that when the outside boat calls for no room and you think it's close you should turn toward them immediately and if you touch then you should protest because you had overlap.

I don't agree with this approach because you should always avoid contact but I've been told this by many seasoned sailors on big boats.

Sometimes people don't understand that the spinnaker counts if it's overlaped against the other boats hull while the hulls are not overlapped.

Remember it's in "normal sailing position" so you cannot let the Kite "flyaway" to create an overlap !

I belive the rule states the onus is on the boat that is trying to claim a change in the overlap status. Assuming your are the inside boat call overlap eary (as soon as it is established).

If you are trying to prove it at the two boat length circle, then you have already lost.

Turning down is pretty much your only option unless you are planning to do a peal at the mark. You are not turning down to force the issue and make contact you are turning down because you cant't stay inside and the outside boat said you were clear.