To the OP, may be your method could be refined a little. The first I found to be working runs like this -
1. Call the regular res line (or 1k line - if u have status) and make a res as usual, citing you have some paper voucher with which you will ticket the res on hold at an airport location.
2. Call web support to do the ticketing with ur eCerts (x2....x6 depending #pax and # of certs)
3. If the agent has no idea abt how to do / refuses, just politely excuse urself and make sure he doesn't do anything to the res, and call back.
I have done this many times for 2 pax for both eCerts and Paper certs.