US overnights different from overseas
You are correct that Cathay allowances exceed the GSA rates in the states, but using the Department of State figures for overseas layovers (which is legal), there is a tax deduction to be had. For exmple, we get a little under $100US for a 24 hour period in HKG, but the DoS rate in HKG for meals and incidentals is $134 for 2007 (over $140 for 2008).