Proportion valve solutions

I have a 1964 Corvette that was fitted with 3/16's brake lines with all drum brakes. I installed 1965 front discs from a Corvette. I installed a 1965 dual chamber master cyclinder, and I'm attemping to install the CPP brass proportional valve and kit. The front part of the valve is set for 3/16's that feeds the front brakes which are now disc. The rear feed was made with a fitting for 1/4 inch lines. I called CPP and they sent me a fitting that will allow a 3/16's line to now be fitted which could be hooked to the rear brake line. However, when you put the flared 3/16's line into the fitting the flare does not look like it would properly seat inside the proportional valve since the intial fitting was for a 1/4 line. I confused as what to do next? Do I have the right brake lines installed? Will this smaller line work in the valve? What can I do?
Thanks Bill.

The flare will seat in the adapter fitting just fine. Use a good flare wrench and tighten it up!