Michael,
I found a source, and it may well be the same source as yours, for that color profile you attached to your post. My reference does not show any more detail than your profile illustration. If you are not able to find any documentation that shows the specific coloring and markings for the right side of that airplane, and given the left side markings show as you wrote:
S1 + GK with the G in the white band.
The right side markings will also read from left (from the tail) to right (toward the nose)
S1 + GK
In other words, the letters/numbers on the fuselages of German WWII aircraft will read in the same sequence from left side of the fuselage to the right side. The crosses will be in the same location on the left and right sides of fuselage. I have more than a "few" references that illustrated this including the Profile Publication No. 76 on the Ju 87.
Now, since that white band can be assumed that it goes completely around the fuselage without any discontinuity at the fuselage vertical centerline, then the numeral "1" will in all likelihood be in the white band on the right side of the fuselage.
There are some very knowledgeable people on this forum that will likely have an opinion regarding the correct answer to you question, but for a semi-scale stunt model of Don Still's Stuka Stunt, the above explanation regarding the "1" being in the white band on the right side of the fuselage should suffice.
Keith