“You can force it to be two sided by selecting “Two-Sided Distance Field Generation” in the static mesh settings.”
Unfortunately doing this severely underoccludes the asset so we are left with a very flat looking foliage asset in our test cases, opposed to an overoccluded one. I strongly suggest considering adding a switch for this or generally looking at the described scenario; if most of the assets geometry has an opaque material assigned to it (what % I’m not sure of), any parts with a two sided foliage material will be overoccluded. Lumen weakens the distance fields when the ratio is within a certain range, but this doesn’t take into account not all meshes will fit in that range.