It's a really easy change:
Line 768 and 896:
change
if(%class !$= "InteriorInstance" && %class !$= "StaticShape" && %class !$= "TSStatic" && %col.getClassName() !$= "fxDTSBrick" && %class !$= "TerrainBlock")
to
if(%class !$= "InteriorInstance" && %class !$= "StaticShape" && %class !$= "TSStatic" && %col.getClassName() !$= "fxDTSBrick" && %class !$= "TerrainBlock" && %class !$= "fxPlane")
There's also some TypeMask lists on lines 709 and 1217 that include terrain and interior that would be updated, but I'm not sure what those lists affect and what the typemask is for fxplane
It's best to PM Space guy to get an official update though