I am going to install better brake housing and see if that makes a difference but I won't be surprised if it doesn't.
I was wrong. I did install new brake housing and it has made a big difference. I put in some Goodridge inner and outer. I've had good results with their gear housing in the past and the brake housing is in the same style, rather inflexible but compression resistant and with low cable friction. To set up the brakes with Campagnolo levers what I'm doing is relaxing the brake levers using the quick release button on the ergo, clamping the cable on the HY/DR brakes, then setting the brake levers back to normal position. This pulls the cable in and shortens the lever travel. With the new housing the brakes are making contact sooner and I now have enormous levels of braking power - if I squeeze hard they're fierce.
Added to the cabling upgrade, and as a spin-off of my umlenker travails, Graeme_f_k of Velotech did a fine job of upgrading my RH ergo with new innards so I'm now rocking Centaur 11-speed.
Goodridge brake cable kit
Road disk bike v1.1 cockpit on a winter solstice ride (it's Southern England, of course there isn't snow)
I revised the gear cable routing at the front of the bike. Bringing the gear cables to the other side of the head-tube gives a better cable line there. I crossed the gear cables over the top tube because the existing way I was routing past the seat cluster is still the best. I'm not sure the crossed cable wins style points but it has a slight practical benefit in my knees not catching the gear cable as they were sometimes doing.