Memory problem with static lit foliage

I’m having an issue with lightmaps on foliage meshes that I’m not sure how to resolve.

Basically the issue is that having static lit foliage results in giant lightmaps that eventually fail to compile / use a ton of memory.

I would like to be able to use vertex lighting in this case to get the benefits of high quality of baked lighting on these meshes but it seems that the vertex lit path has been removed form UE4? This would be really useful for this case.

Additionally I have tried using the new volumetric lighting path for foliage (using force volumetric in the foliage settings) and that appears to do nothing. Then the foliage seems receive no cast dynamic or static shadows.
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Above is static foliage with lightmaps. Can’t use due to eventual memory overflow

Above is movable foliage with “default” static lighting. Doesn’t seem to use the volume lighting correctly. Compare to the floating cube which is a movable static mesh and it being lit red.

Above is the results with “Force Volumetric” static lighting using either movable or static foliage meshes.

Any help as to how I could approach this would be much appreciated.

Regards,