On the internet, I found that Superstrip100 contains a thallium compound and, I would guess, lead acetate. These are added to lower the rate of attack on the base metals, primarily copper. I don't have specific experience with SS100, but I have used TechniStrip AU, a very similar product (I think) made by Technic. It was virtually impossible to precipitate the gold from the TS AU using zinc because of the presence of the thallium and lead. Technic sold another product (which I think is nothing but sucrose = sugar) that supposedly could be added to the pregnant TS AU solution to allow the gold to be plated out but this didn't work well either. We had about 1000 gallons of pregnant solution and ended up using a dangerous and very involved method with sodium hydrosulfite. On this link, there is a method of using sodium hydrosulfite to get the gold by Till_Eulenspiegel.
http://www.sciencemadness.org/talk/viewthread.php?tid=5700#pid80768
The moral of this story is to avoid most types of commercial strippers if you want to easily get all the gold out. These products are designed for platers to strip faulty plating, without damaging the parts, so the parts can be re-plated. The platers usually ship the pregnant gold stripper back to the manufacturer for refining.
If you look, there are most probably brownish flakes in the dry SS100. This material is m-NBSS (called meta nitro benzoic acid sodium sulfonate and various other technical names). A common name for it is Ludigol and it is used primarily in the textile industry. When combined alone with sodium or potassium cyanide in the same weight ratio (and operating conditions) you used to make up the SS100, it will strip gold readily and the solution can be easily zinced to obtain the gold. It does attack the copper a little more, but this, along with the excess zinc that was used, is easily removed from the well rinsed zinced gold sludge using weak nitric acid (UNDER THE FUME HOOD!!!).
I noticed that the SS100 manufacturer has another product called Superstrip108, which is said to contain no thallium. I would guess it only contains m-NBSS and, therefore, it may be zincable.
http://www.chestech.co.uk/processes/MetalStrippingProcesses.html
In general, no matter what stripper you use, plating is a poor way to get all the gold (or any other metal) in a batch situation. As the metal(s) plates out, the concentration of the metal(s) in solution decreases. As it decreases, the deposition efficiency decreases and part of the current splits water (and/or, performs other cathode reactions) instead of depositing metal. At some point, virtually all of the current splits water and some of the gold (or other metals) always remains in solution. Also note that, in a cyanide solution, the gold is in the form of a negative complex ion. It is repelled by the negative cathode instead of being attracted. Therefore, when the gold concentration gets low in the solution and there isn't excellent agitation to mechanically provide fresh gold ions to the cathode surface, the system will lean towards the splitting of water (or other reactions) at the cathode.