Joypad mapping to keyboard

[atoone]

Running under Retroarch, Fuse 1.6.0 on the Anbernic RG351 -

Can only map Sinclair keyboard if Port 1 Control is set to Mapped Port 3 (Using Port 3 doesn't work, even if Port 1 and Port 2 are set to none) - but this looses the ability to map a button to the keyboard overlay option.