Looking to build a baffle on a BT-80 based rocket

That's exactly right Tim.  The flat sawed off parts on the forward bulkhead allow the shake-out of debris.  It's the usual round bulkhead but with flat cuts:

 

The coupler (in this case a jt-60C receives the output from the 24mm white tube.  I epoxied a disc to the bulkhead to help hold the coupler in place.  All wood surfaces are also coated with epoxy.

And btw Ken is quite right... it's a "chore boy".  ONE chore boy can be pulled apart to make three or four replacements for the Aerotech baffle!  For a 29mm tube the weight isn't excessive... the one I have for the auction arcas kit I bought comes in at 7 grams... The thing is they'll collect crud and need to be replaced... AND they start to rust and disintegrate too!   I replace mine on my Aerotech kits every 6 - 12 flights.