The Yana Shiki 2" bones you find on ebay lower it about 2.25", maybe 2.5" if you drop the shock down to #2. My wife and I together weight about 350 pounds and I've only bottomed out twice with those on. Both times were not in places you should normally find on the road, like the end of a section that was being paved that had a good 4" dropoff and no warning.
Grind the bolts off under the fender that are right over the tire. You can also remove them from above and shorten them. If you don't they will cut grooves in the tire if you bottom it. With them cut off, even if you bottom it it doesn't do anything other than make a slight noise.
Or do as I did and get the wife/significant other her own bike, then you can lower it as much as you want.
