MinimOSD_Extra_Plane_Pre_release_Beta was improved, please see MinimOSD_Extra_Plane_Pre_release_Beta/README.txt for changelog and build instructions
Prebuilt binary for plane: Released/FW & Char/MinimOSD_Extra_Plane_R8??.hex
For this to work well (it can still work ok-ish without), it's better to set SR1_RC_CHAN 5 (although it can work with the default of 2, it's just more picky about timing). If your OSD board is plugged into serial2 instead of serial2, then change SR2 instead.