A Lateral MOSFET Power Amplifier Design Version 1.1

[Indiglo]

I started over my board layout checking progressively my traces length in the tools and finally, with my board at 10 inches wide, I still can use the 80 mils trace width I was using for the ground and the rails over a 10 inch length without problem... See below, I can travel more than 8A over 10 inches!

I noticed an error in the calculations, you have set the Options for Base Copper Weight to 2oz and Plating thickness to 1oz, this gives a total pcb track thickness as 3oz.
You can either set Base Copper Weight to 2oz and Plating thickness to Bare PCB or set Base Copper Weight to 1oz and Plating thickness to 1oz.
The above changes is assuming the pcb's are being ordered as 2oz.
Setting the copper thickness to 2oz changes the current from 8.0015 amps (3oz) to 6.3174 amps (2oz).