I've done this over 10 times now. Fly UA in upgraded C from USA to SIN, rest up in the transit hotel, then take the 9am Silkair flight. The Silkair flight goes to both Cebu and Davao, and alternates in direction on different days. So, if you want nonstop service to either city, you may have to adjust your dates by one day. The flights have been running $4-500 USD, and you get to completely avoid the horrible mess that is MNL. UA interlines baggage with them too.