I think we talked about this on oldtärck but my favorite way to set up vntg cantis is to ditch the straddle, use rear cable hanger to make a link wire, and install a ball bearing roller at the crown. ATMO it makes it act/feel more like a mini-V brake. I think some other people here might have tried but I never heard back so maybe it only works for me.
A mildly interesting feature of this setup is you can put it on the back of the fork without any clearance problems. Tie it together with a U-brace and it becomes a super effective rim brake