I don't know if anyone ever got back to you, this thread moves really fast, and I think there's a lot of skimming to try to stay caught up so your post might have been lost.
Here are my thoughts in your situation. Have P1 cancel CIP*, this will free up some credit line, then P2 refer P1 to CIP in April (30 days after closing 1st CIP). After P1 has CIP#2, then P2 cancel their first CIP and P1 can refer P2 to their 2nd CIP (again 30 days after closing). Since P2 just opened a Chase card 2/19 it makes sense for P2 to wait til May-ish.
General guidelines seem to be no more than 1/30d, 3/6mo and 4/12mo for Chase velocity. Someone else might weigh in with different velocity numbers.
You've done a great job so far!
*Apparently holding a CIP doesn't exclude you from getting another one, it's just I figure you might want to reduce CLs anyway before applying...P2 will have their AF coming up soon anyway.