Fed up with water dripping into the boot & seeing the addition of several small circular openings in the latest Model 3 rear screen rubber seal, I purchased this single hole paper punch
https://amazon.co.uk/gp/product/B000I5SAPY/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 & put five equally spaced holes into the seal on mine (two can be seen in top pic below).
Care needs to be taken in twisting the seal to punch downwards & away from the glass to avoid catching or chipping the edge - quite easy but be aware & exert gentle pressure beforehand to check nothing is touching (I'm led to believe that to confirm Tesla glass is within tolerance, tap anywhere with the head of a pin to crack it).
On closing, pouring more water on the rear screen & opening the boot, it immediately trickled through into the trough below so it seems to work. Although I say it myself, the holes look as if they are OEM.
(small thin protruding 'tongue' - middle LH side of picture bent flat before use)