Panasonic uses a 48-bit protocol that is very similar to the NEC IR protocol. You could adapt the NEC protocol to your needs.

If your header and end-of-packet bytes serve no other purpose you can drop them, using those that are built-in to the NEC protocol. Here's a URL to documentation for the NEC protocol.It uses a 9.5mS pulse followed by a 4.5mS space as the preamble or Start-of-Packet and a 0.5mS pulse followed by a 40mS space as End-of-Packet. I use a 0.5mS pulse followed by 1.5mS space as digital 1 and 0.5mS pulse followed by a 0.5mS space as digital 0. I would send your 4 data bytes plus one checksum byte for error detection.

Experiment to find whether you can send just one copy or need to send multiple copies to guarantee clear reception.