2A LED Driver for 4-17v range

Coming back to this, I'm also using it in a lower current application from 0.1 - 1.5A.

I've upped the sense resistor a bit and played with the resistor dividers but I can't make the regulation that accurate. By 1A it's 10% down.

Another question. I get less ripple if I remove the hysteresis provided by R4. Is R4 there to:

a) bump the nominal voltage provided to the comparator pin so that the value is well above the minimum input level
b) prevent the comparator switching at the maximum speed of the inductor charge/discharge, therefore minimising fet switching loss (at the expense of ripple)
c) something else