The "cleaning vinegar" (it was so labeled) did open the pipe enough to flush it, but not enough to flush easily and it's already plugging up.  I ordered a bottle of "Sew Clean" to see if that works.  

Maybe the best “solution” (pun intended) is to prevent the urate deposits from forming. The original owner, also a physician, cautioned that every flush should last 10 seconds, counted religiously. We’ve followed his instructions and have never had any problems with the heads.
Drew
SY Revelation SM390
Carloforte, Sardinia