I'm looking at a flight from LA to Guadalajara, but even though it's a relatively short direct flight, I'm still kinda worried about losing my luggage. I'm considering buying the "Zero" fare and adding the 15kg carry-on which is similar price to buying the "Extra" fare which includes 15kg check-in, but I always worry with low-cost carriers that they'll use any excuse to negate an add-on that I paid for. I think this is supposed to be an Airbus 320 and normally my backpack fits in overhead compartments of international flights, even if technically the measurements seem slightly larger. (A security guard at JFK once forced me to show her it fit in one of those sample "cage" things even though the airline check-in had already let me go, but it somehow squeezed in!)

Anyone have experiences with Viva Aerobus staff in LAX and add-on luggage sizes that are toeing the line? Or do you think Viva is trustworthy with check-in bags for a short direct flight? The flight I'm looking at arrives way too early in the morning to check in at a hotel so I wouldn't be pressed for time, just afraid of the bag being lost completely.