You may want to take a look at the HIpshot line of tuners. They do have open back tuners with 18:1 ratios, and they are very, very smooth in tuning action, and rock solid in tuning stability. Only thing to be careful about is that the tuning shaft size may not be rignt for you ( I think they come in 10mm shafts (mostly good for imported guitars) and in 8,5mm sizes). I haven't used them on an acoustic yet, but do have one set of locking open back tuners on an Epiphone Les Paul, and another set on a Squier Stratocaster. Love the tuners in both cases, but these do have 10mm tuning post holes. I used the UMP plates on both guitars, and they worked great. If the tuning post holes on your guitars fit, the tuning post spacing won't be an issue, as the UMP plates allow the spacing to vary, and do not require re-drilling the back of the headstock. Also, even though these are individual tuners, the UMP plates sort of make the tuners look like 3 on a plate tuners. Lastly, there are like 18 different tuner button options, some of which don't really apply to acoustics (the black T style buttons come to mind) but most of the standard type buttons are available (large and small oval (sometimes called butterbean) and metal and plastic keystones), as well as chrome, gold, and in some cases, black. They usually run about half the price of Klusons or Gotohs.