I have a PC that is building towards crafting constructs, yet the rules about it are different depending on where you look. Ultimate Magic says the DC to create any construct is 5+CL, but if you look at specific constructs that were around before Ultimate Magic they have difference DC's to create. For example an Iron Cobra has a CL of 7, and listed DC to create of 15. So does my PC need a 12 or 15 to craft it?
If a construct has a listed DC use that. The 5+CL is a default for where no DC is listed.