With oil drain plug tightened to spec (37 lb-ft / 50 Nm) and a new washer, I'm still getting some weep. I've even tried "over-tightening" it to a hair over its torque spec, but still woke up and seeing "weep".

Absolutely no puddle of oil on the ground.

Pic is of my paper tower "blotting" the drain plug area after leaving the car overnight. You can faintly see the rings of fresh oil.

Any cause for concern, or just leave it and replace both plug and washer 5000kms later? What's a good remedy?

 

I would leave it and then replace with new plug and washer next oil change. Flat sanding the washer before install on 320-400 grit sand paper on a surface plate ensures no leak, make sure to clean after sanding before installing. You can do this with re-using the same washer.

 

I would leave it as well until the next oil change. Also, I would use an OEM washer if you didn't before.