Hi Peter,
With my former-PC hat on, let me chime in:
First of, I do not think this specific case needs formalisation as there is NO need to reserve a slot before neither PC nor RIPE Chair even know that there is a need or request for such a discussion at any given RIPE Mtg. And in fact PC Chair and RIPE Chair are in constant coordination for such stuff if they surfice.
Secondly, note that we did asked for a 30 min slot for a status update presentation and that is well inline with PC's jurisdiction, alloting a 30mins, and finding the best place in the Plenary Programme in the light of all other submissions they receive for the particular meeting. If we want a wider discussion and that needs more time, yes, HPH will get engaged with that request anyways, as I explained above.
I hope this clarifies the matter in hand.
Filiz