Nice write up Earl! You’re right, there is a little bit of loss around the sliding portion of the gates. I haven’t seen it make a huge difference in my setup, but every little bit helps!  I’ve also used 4” S&D and love it. 

As a consideration behind your lathe: if you extend the S&D a bit further and make the turn in 4”, then use the segmented 2.5” as a directional ‘boom’ to point the orange nozzle towards your work, you’ll have less loss. I do something similar (but don’t have a pic). Honestly, it’s not going to help with chips, but it’s a world of difference when sanding on the lathe!

Nice write up. Thanks. 

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".