Mercury does not erase what you say on October 19. That is the loop worth closing first. Mercury turns retrograde on October 24 at 20°59′ Scorpio, nearly the exact degree it occupies on October 19 at 20.93°. A station so close freezes new information — it does not retroactively delete a clear sentence. Speak on October 19, 20 or 21, and the talk has a fixed record before the review begins.
The days between are where the opening tightens. The Moon leaves Aquarius for Pisces on October 21 at 13:35 UTC, softening the tone but also loosening the edges. If the limit needs saying in flat words, say it while the Moon is still in Aquarius. After that, the talk drifts back toward feelings, and feelings are what got rescheduled in the first place.
Then the season opens. The Sun reaches 0° Scorpio on October 23 at 09:37 UTC, conjunct retrograde Venus at 1.21°. The Moon is in late Pisces that morning, and its trine to the Sun is too wide to steady anything. Nothing about the sky on the far side of the ingress makes the talk easier.
Here is what changes if you speak now. The negotiation happens on the record. When Mercury stations, you get to compare what was agreed on October 19 against what the review surfaces later, instead of arguing about what was never said. That is the practical payoff of moving early, and it is the whole difference between a boundary and a wish.
Venus, retrograde until mid-November, keeps the value question open longer than four days. So the October 19 talk may not be final. It doesn't need to be. It needs to exist — a date, a figure, a sentence that survives being quoted back. Everything the retrograde period reviews afterward has to review something.
If the answer is that you cannot yet write the ask in one sentence and the consequence in another, don't force a speech. Write the one line you can defend. Send it October 19 to 21, before the station. Scorpio season rewards depth. It does not forgive silence dressed up as patience.