Thanks for the input.

Incoming data is standard 9600,8,N,1
Interbyte delay 80us
Packets are 5 bytes long.

1) Header (I know what this will be so could skip/lose this byte)
2) Length (5)
3) Data 1
4) Data 2
5) Checksum (I know the header byte even if it is corrupted/lost so can still calculate the checksum)