Two sided foliage Shadowmap

So i guess i have a good example for two sided foliage material which is the clothy lamp shade of my lamp. the lamp shade itself is a one sided only mesh with normals facing outward, so naturally i also checked the ‘two sided’ box. it all works looks nice and fine UNTIL the lighting is built.

the inside (backside normal wise) is completly unlit. but in lightmap density mode its clear why… no lightmap at all?

is there a way to set a SECOND lightmap to the backside of a two sided object? what gives?