In a more general sense, have those of you with multiple passports encountered any extra interrogation? I've been debating whether I can push back a US consulate visit for extra pages a bit by using a fresh passport. If, hypothetically, SIN basically fills up my US 48-pager and I present another passport with no stamps in it at HKG, the immigration officer will know I had to use some other document to get to that point. I just don't know whether anyone cares -- or, worse, if it's not permitted under the laws of some jurisdictions.