The TYGA subframe is designed for one rider only. It's is not designed to have weight at the back, other than the battery and PGM.
If you try to do this then you're on your own. Chances are the subframe will bend, or worse than that, actually break and unload your passenger into the rear wheel at high speed, which won't be pretty.
The YSR80 was designed for loading Soi 8 girls on it.