Dual MOSFET latch circuit

I've seen several circuits on the internet similar to this one. It is a dual MOSFET latch circuit. It can be used to turn a load on and off using a single pushbutton.

I suppose this works for the people who uploaded the circuit using the specific MOSFETs and resistor values they described but I had trouble getting it to work reliably.

How it works:

When power is supplied to the circuit the gate of M1 is pulled high through R1 turning it off. M2 should also be off. C1 starts charging to Vdd.

When you press the button C1 provides a high voltage to M2 turning it on. This pulls the gate of M1 low turning it on. The voltage at the drain of M1 keeps M2 turned on. When the button is released C1 discharges through R2 and M2.

Pressing the button again while the circuit is on pulls the gate of M2 low by the now discharged C1. With M2 turned off the gate of M1 is pulled high again by R1 turning M1 off.

I have been studying this circuit for a couple of weeks and found a few things that make it work better for me. I added a resistor from the gate of M2 to ground and I figured out how to select values for all of the resistors. The new circuit:

R1 and R2 bias the gate of M1. They should be chosen so that the voltage drop across R1 is less than the minimum Vgs(th) value. This makes sure M1 turns off.

R3 and R4 bias the gate of M2. The addition of R4 ensures that the gate is pulled to ground when the circuit should be off. The values of these resistors should be chosen to set the gate voltage just above Vgs(th) max to make sure M2 fully turns on. In the original circuit when pushing the button to it turn off C1 charges toward Vdd through R3 until M1 turns off. If C1 can get enough charge faster than M1 gets turned off then the circuit stays on. R4 causes C1 to charge slower by reducing the target voltage giving more time for the MOSFETs to finish turning off.

After adding of R4 and properly biasing the MOSFET gates this circuit works reliably for me. I plan to use it in a few projects I have in the works.