(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fbottleheadnginx.bottleheadcorp.netdna-cdn.com%2Fwp-content%2Fuploads%2F2014%2F01%2Fmainlinehd800.jpg&hash=2bdd49d68e1d87de04d2f0a1ed7bbceba04181bd)
It's too difficult to hand build a reliable connection with those terrible plugs. My cable breaks each time we take it to a Head Fi meet. They really need a molded plastic strain relief.
... thinking out loud ...
Since your 3/4 of the way there...
Since they can be disconnected, how about successively larger heat shrink layers, cut about .5 millimetre shorter each time and lined up at the top? Enough layers should help to keep that bend radius in check. Enough heat may even blur the line between layers.
The disclaimer being - I've never tried layering heat shrink.