John, thanks for addressing my question. Just so I am clear, in reading your reply it looks like my combination valve does have a proportioning component, but it provides the pressure applied to the rear brakes as a predetermined fraction of pressure applied to the front discs, in order to prevent premature rear wheel lock up.

Do I have this right?

If this is the case, it doesn't sound like the proportioning component is a bad thing.

Or am I wrong? Do I need to disassemble and modify mine?

After replacing every component in my brake system, changing to 80mm front calipers and 1-1/16" mid axle wheel cylinders, and bleeding with a Hupy style pressure bleeder, I am still not impressed with braking performance

Thank you.