Bernie,
That's a good looking linkage. I came up with 2 designs that provide geometrically perfect action for 4 ida's with external fuel feeds, yours is one of them. I'm going to try a single bellcrank with the inter-connect levers first however. If I'm not satisfied with that, I'll make a dual bellcrank system like yours.
Also, I designed and made a similar bellcrank plate for my system, have yet to get it polished but it turned out nice, 11 minutes from design to part, no drawings, isn't laser technology wonderful. Here's a pic...note the logo.
Chuck