If 837 is on time then you should be ok. However, 837 hasn't done too well for me the last couple of flights: had a 5 hour delay a couple of months ago and a 2 hour delay before that. As for Cebu Pacific, don't bother trying to carry-on anything bigger than a small bag, they will make you check it. I know you can inter-line your luggage between UA and 5J.