Hi Russ, I was in the PI earlier this year. I flew with Air Phil Express as well as Cebu Pacific. I managed the excess baggage well enough with a combination of sports allowance and prepurchase of excess baggage. Rules may have changed, but I'm sure Cebu had a sports allowance at that time. But I found the prepurchase option to be very useful and economical as well.
Sometimes rules are different just based on where you buy the ticket from. I was in the PI when I did my Manila - Coron ticketing, as well as my excess baggage add ons.
Also, as a special note, I was booked to fly Air Phil Express from Manila to Coron, but I had to cancel that and fly Cebu, since Air Phil did not allow excess baggage on that route even with payment (or they did not guarantee it would go on the small plane with me, maybe follow later depending when the next plane had enough space...). Cebu worked for me, but they charged me at the airport for being 1 kg excess. I read somewhere that Cebu are sticklers for charging for any excess, however small.
Hope this helps.