Ercoupe Braking

The Alon is still new to me but I believe the brakes are Cleveland. The rotors look good. The pads look like they have been cut out of some soft braking material, but haven’t seen that much use although they are partially shined up. The master cylinder is original equipment, as is the short the rubber line leading from it along the firewall.

My first question is do you have the original brakes or upgraded to Cleveland brakes, rotors, pads?  Not sure what types went into Alon produced aircraft.

I was in a frisky mood, and testing the brakes on my Alon for Maximum Braking ability, using the hand brake and pulling on it hard while still trying to maintain directional control on rollout. I must say I was somewhat underwhelmed with its braking ability, both on grass and on pavement. Try as has I could, I could not get the wheels to lock up, or the tires to squeal. I estimate I was getting 65 to 75% of Max braking. I mean the braking is OK, but a lot of runway is being left behind with this moderate performance.
My question, - Is this the Normal braking ability for an Ercoupe/Alon?
- If not, any thought on what is causing it?
Is it due to a weak Master Brake Cylinder, worn pads, of possibly air in the line, and how do I diagnose air in the line or a soft Master Cylinder?