Try this.
Seeing as the 19's are rated to flow 19% more (18.75 to be exact) than the 16's. Try setting the low setting to -19/-20 and taper it off up to 0 around the 4500rpm mark.
Something like this
1k**1.5k**2k**2.5k*3k*3.5k*4k*4.5
-20*-20**-18*-16**-12*-8**-4**0
See how that works for you....
