The CE680 is limited on Hawaii legs, contrary to all of the opinions due to fuel limitations in the event of a rapid decompression. Single engine operation is not an issue.
LAX or SFO to Hawaii in the CE680 with winds of more than 45-50 knots (depending on azimuth) will only allow for scant fuel reserves (400-600 lbs.) after an emergency descent to 10,000 feet per the AFM.
There are operators (like the Cessna demo. pilots and the pilots with Citation Air) who will dispatch based on a flight profile that stipulates IF you have a rapid decompression, you will descend to FL250, fly for 180 minutes while the pilots and passengers deplete the oxygen supply, and then descend to 10,000 feet. This totally disregards the Sovereign AFM; there is no procedure for this. What would you breathe at minute 181 if the cabin/cockpit fills with smoke?
Med Aire and three FAA AME's that I have spoken with strenuously advise not to follow a procedure such as this due to trapped and evolved gas issues and other barotrauma that can occur. The non published procedure also assumes that the passengers in the back actually survived the mayhem of an emergency descent and actually got their masks on and secured with adequate flow.
Bottom line- do not dispatch unless you can have at least 1000 pounds of fuel over the depressurization ETP. This equates to 30 minutes of fuel...basically VFR fuel requirements after an emergency.