If you’re using them as straight needles, I get that you screw a cable on the needle, then a button on the end, but you hafta use 2 different size cables for 2 needles? Now that’s just gonna bug me, and I’ll just hafta order another 12" cable I guess! 
Already a Boye Needlemaster Question!
why not just connect them to each other and use the circ as straights that way?
I guess I could do that…you mean sort of like you’re making a blanket or something and just go back and forth?
you betcha…you can do that with anything that you knit flat…doesn’t have to be blanket size at all.
Thank ya dear!
And I don’t think it would be absolutely necessary to have two equal lengths anyway, just make sure the shorter one accommdates the width your project, but like brendajos said, but you can even do narrow stuff flat on circulars.
There’s no need to make 2 separate needles for anything…just put a needle at each end of one cable, and knit back & forth.