Not sure what you are trying to achieve with the home made brackets but you can buy proper Yamaha adaptors so that your Music rack and/or your Tyros speaker brackets can just slide on and off

I got mine from a German site for a few Euros - They'll post internationally to you for a few more euros.

This makes transporting the Tyros easy as I no longer have the brackets protruding from the keyboard and just slide on the music rack brackets etc into the close fitting adaptors fitted instead

KF