After just a few runs I recognized that the left foot pedal is very high off the floor.
If you have run the machine you notice that the pedal needs a full push; if you make a slow or partial pedal actuation the machine reacts slowly and without the necessary force or speed to make a firm stitch.
The problem with the amount of pedal travel is how far off the floor your toes are when the pedal is full up. Basic Human Factors dictates that the operators ankle angle should be no less than 85 degrees; or the ball of foot should be no more than 5 degrees off the floor as measured from the heel.
With your left foot extended as high as it needs to be (without the foot
pad) you are almost standing on one foot, which doesn't help you stitch
concentration at all! Stitching is such a concentrated effort and so pressing the pedal needs to be as effortless as possible. All of your thoughts should be on the next stitch and not on how cramped your left foot is.
In classic automotive occupant packaging the drivers foot is shown at 85 degrees of flexion. We place the accelerator pedal so that when the car is at idle with no pedal deflection (waiting at a traffic light or stop and go traffic) the ankle angle is no more than 5 degrees from perpendicular to the lower leg.
Also I forgot to add this YouTube that helped more than just about anything: Instructional: McKay Stitcher
Thanks to grahamsshoeservice
Foot pedal foot rest fine tuning; I added a slope to the end of the 2x4 making it easier to tip my toe down while leaving my heel engaged