Pwm solar Charge controller

I am working on a pwm charge controller. My charging current is at 10A and wish to amp it up to 20A. I am using an IRF9540 Pmos and i have narrowed my search down to an IRF5303 Pmos as a replacement for the same. I have attached the schematic in the above link. my question is can i just replace the old one with the new one or do i have to provide additonal circuitry? please do help. Thank You.

Well there's no inductors in that, so all your PWM can do is REDUCE the charging current - but regardless of that the charging current is basically dependent on the available power from the panels, if you want to double the current then double the number of panels.

As far as adding inductors goes, by doing so you could make a boost converter, and add an MPPT system to maximise the power from the panels.

Doubling the current probably means increasing PCB tracer sizes and/or connecting wires. Are you modifying an existing piece of equipment or designing from someone else's base design?

I would think the gate drive circuit would need improving, using a 10k pullup for the gate will be kinda slow, an active pullup would probabyl improve power dissipation in the fets.
Also without any resistance in the gate circuit turn on will be very fast possibly vausing emi, and current spikes will be high.