Keep the top screen clean so the stereoscopic 3D experience is not interrupted by elements of the HUD poking you in the eye.
Naive way would be to draw anything currently flagged as 2D to the bottom screen, longer term would probably involve changing the construction of the display lists to fully separate 2D/3D.
2020.09.07 edit:
Naive method has been implemented on 3ds-minimap branch when the ENABLE_N3DS_3D_MODE flag is set.
Keep the top screen clean so the stereoscopic 3D experience is not interrupted by elements of the HUD poking you in the eye.
Naive way would be to draw anything currently flagged as 2D to the bottom screen, longer term would probably involve changing the construction of the display lists to fully separate 2D/3D.
2020.09.07 edit:
Naive method has been implemented on 3ds-minimap branch when the
ENABLE_N3DS_3D_MODE
flag is set.