Yesterday I just finished connect APM2.5 with MinimOSD v0.1. You don’t need to solder extra UART0 pin on the edge of APM2.5. Just use the telemetry cable come with APM. *Becareful* to check voltage/ground pin before plug it.

Please also check your MinimOSD firmware. You have to use most current firmware with MAV1.0 support. Download from here and firmware upgrade instruction.