The "Original" SBGH was an evolution of the HOVERMAN and earlier CHIREIX Antenna, wherein all Diagonal Elements were the SAME Length at SAME 45-deg Angle. Unfortunately, since they were "Single Frequency" Resonant designs, none of them had enough Bandwidth to cover the "original" UHF Band from 470-806 MHz, although the HOVERMAN had almost enough Bandwidth for the "new" UHF Band (470-698 MHz). When the Hoverman's Outer Elements were shortened nearly 2-inches and moved to the Horizontal, it became the "Original" SBGH:
The Optimized G-H Antennas found on nikiml's website eliminated the CONSTRAINTS of Equal Lengths at 45-deg Angle, allowing different Lengths at arbitrary Angles. This allowed "Stagger Tuning" to widen the Bandwidth [resonating at different frequencies], with additional "Degrees of Freedom" to facilitate Optimizing the Gain and SWR Performance.
In nikiml's nomenclature, "0" after the name (e.g. GH0) indicates NO Reflector, GH2 means 2 co-linear Reflector Pairs, GH4 means 4 co-linear Reflector Pairs, etc., as shown in each "MODEL". An "n" after the name indicates that it includes additional Elements (e.g. Top Hats that are passively "coupled" to the GH) to improve Hi-VHF Performance.
If you download each 4nec2 file, you can see the X,Y,Z Coordinates, although it is difficult to "decode" what is going on. It would help to correlate SYmbol X,Y,Z Coordinates and Element Lengths in the 4nec2 file to the various wires in the MODEL on nikiml's website, by selecting a particular G-H Design Number and then Select "MODEL". You can select (default) mm or inches in bottom-left and view in bottom-right. Roll over Element Ends and Middles to see X,Y,Z and Lengths respectively. Angles are NOT provided...nor should you "need" them, relying on X,Y,Z Coordinates.
You might want to compare to the fol. "Free-Form" [i.e. "Stagger-Tuned"] FF4 4-Bay Bowtie and FF6 6-Bay Bowtie Designs, with NO Reflectors:
Note that both of these improved Bowtie Designs is a significant improvement on the GH0 (which provides 7.8 to 11.9 dBi Gain), which is not included in below [NO Reflector] UHF Comparison Chart: