Still wondering in this story But I will try to understand
I think it's pretty straightforward, so i bought a copy TCS original Yamaha belly pan pan from Poland that was supplied with no mounting brackets, and I was stuck as to how it fixed on the bike.
Low and behold some kind foccer took some pictures of his that he was selling a few years back so I screenshotted them to give someone else an idea if they decided to buy the same one.
Looking at the bottom frame mounts there's not many things to buy on ebay like that so I opted for 'P Clips' and will use rubber damping spacers so it doesn't vibrate.
The top ones can be made out of 2bits of steel flat bar