Thanks for the replies folks. Tonight I measured the fork drop out width at it's widest point (lawyer tab to lawyer tab) which was 124mm. I then measured the quick release with the end cap "just engaged" onto the threaded end of the skewer to be 125mm. This give me about 1 turn of margin.
What I need is either a skewer with a longer rod, or an end cap that has a shallower recessed area for the spring.
If Mel at Tandems East can't help me, I'll reach out to Co-Mo and to Spinnergy.