So, being the paranoid type that I am, I went to the SQ counter at SFO and asked. I'm fortunate that I live less than 15 minutes from the airport. I told them that I was transferring from SQ to PR in HKG and the tickets would be bought on two different itineraries.

The person, disappeared to the back for a few minutes to ask the supervisor and then came out to tell me that it could be done and 95 minutes was "plenty of time".

Hope they remember this conversation in January...