Anytime...
RPRF maybe sent anytime, either with the initial apps, or during the 2nd stage of docs submission, or even still -during the meds request. Actually, if one hasn't submitted it till meds, the CHC shall ask for it while sending the med papers. Sending it then is quite fine. Many do it, I did it & probably 80% do so too.
It won't make any diff in your case processing timeline.