If it were me (also 7a) I would wait until mid May. Water a day or so before grafting if it’s been dry and keep an eye on it if you hit a drought.
Your prior failure could have been for a host of reasons, least likely of which is too much heat.
I would not recommend doing a bark inlay where you try to have 2 competing leaders. It likely will not turn out well. Pawpaws like to have a strong central leader it seems.
Others may disagree.
Good luck!