Did some more filter testing.
I’ll preface this with I’m not a massive filter drinker.
I reground the duo espresso to 18 as it was right.
Using a clever dripper
Zero
Draw down 3:27
Duo espresso burr
Draw down 3:33
Duo filter burr
Draw down 3:23
Zero- dry, visible film, bitter after taste
Duo espresso burr - good mouth feel, more acidic, slight bitter sweet aftertaste
Duo filter burr - sweeter, sweet after taste, more clarity cleaner finish