what type of cleaning fan do you have . the chevron type work the best with these chaffers as they need alot more air . Were talking volume not veolocity the chevron style delivers alot more air but not a high veolocity blast like the old paddle style fans did . They say that you can't blow grain off a airfoil chaffer because the air is coming straight up not like a peterson type chaffer but you have to load the chaffer properly or the air will be lost on the part that has no chaff and the grain will just sluff off the chaffer with a thick layer of chaff . So do some quick kills and see how the seive is loaded if heavey on one area try to eaven it out . the chaff should be thinning out by the last foot of seive if not could use more air . should never have chaff coming off the seive in bunches . I know that the airfoil chaffer need more fan speed than a peterson type seive but trial and error is probably your best bet and a bit of combine chasing with a checker seive .