Conversion project more challenging rather than build new FPSO. Many technical issue, clarification, un-compliance spec, unpredictable situation, surprise condition, unplan situation can be happen on conversion project. Some contradictory requirement (Company spec, Class, regulatory, government, etc) is require much time to solve specially some Company or Contract is not flexible to changing the standard.
But some of project have completed on schedule because EPC Contractor have good experiences on solve the issue.
Mostly issue is typical. Not much is new. So from my perspective of view, experience and competency is important factor for conversion project.