Since the SESG is already lowered 1" compared to an Ultra, dropping it even more is not likely to be a rewarding experience. If you do it with shorter shocks or those lowering brackets some folks sell, you may very well run into clearance problems, both tire to fender and frame/footboards/hard parts to ground. Shorter shocks tend to ride like crap as well.
Using an adjustable air ride system with an on-board compressor can allow you to drop the rear for posing at the local hangouts, or moving the bike around in the garage, but it's not much of an answer if what you are looking for is an easier reach to the ground every time you stop. You don't want to actually ride with the rear end slammed, and I don't think you could constantly bleed off and then jack up the pressure every time you stop and then take off. Riding with the rear end slammed is unsafe and is also likely to cause some fairly serious damage.
If you want to lower the bike just to look cool, my advice is to forget it. If you want it lowered because of short leg syndrome, my advice is to first look at changing the seat and your footwear. Those items will be less expensive and won't screw up the ride quality or handling.
JMHO - Jerry