And quite the rabbit hole it is - I've been reading old articles most of the morning. Interesting story on that bike.
If I remember correctly, the secret to making those Diacompes work well is to keep them clean, well-lubed, and have a floating hanger (with lots of grease to let it slide on the straddle cable) and then Diacompe came out with the roller hanger (which is still available):
https://velo-orange.com/products/gran-compe-straddle-cable-hanger
Peter - I built my first "gravel bike" last year from an older cyclocross frame. I selected 35mm tires thinking those would have to be plenty soft and find myself wishing for wider on gravel around here. Maybe your paths are better packed than those I try to ride and that beam will surely take the edge off. Am interested to hear how that all works out for you.