Thanks for the bump.

We foam the lower undercarriage and it expand and fill up the beams. Rain water does not enter thus does not need to exit. I don't know what you trying to imply but after the foam is injected into the beams , no rain water will enter, end of story already. Its not like we flood the door with foam or someplace else which have exit point for rain water, in the chassis undercarriage there is no exit point or entry point for rain water. The holes at the undercarrriage's beam is for re-enforcement of the beams if according to engineering terms. So, there is no answer to your question.