Help understanding Texas bridge formula

I just bought a tandem dump truck and need to register it tomorrow. It has a 20k front axle and 46k tandem. Texas limits a single axle to 20k and a tandem to 34k so that puts my max at 54k.

However the center of my front axle to the center of my rear tandem is 20'6" so I think I am limited to 51,000 per the bridge formula?

Should I register the truck for 51k?

I also plan on getting the annual overweight permit which I think allows you 10% over on axles and 5% over on gross?

Basically just want to make sure I tell them the right weight when I register it so that I can haul the maximum amount possible.