Feathered Beams + Make-Moment Confusion

[Joey Di Nardo]

Hello all, I am currently dealing with this measure:

|%26
r8\mp
\times 2/3 { wbh16 wbh r16 }
\override Beam #'grow-direction = #RIGHT
\featherDurations #(ly:make-moment ? ?)
{ wbh16[ wbh wbh r16 wbh] }
r2.
|%27

And I'm a bit uncertain as to how to manipulate the make-moment in order to not 
return an error. I'd theoretically like to make the feathered beams speed up, 
all in the place of a quarter note.

I am currently getting a barcheck error no matter what values I place in 
make-moment.

thanks,

Joey