I was involved in a job recently where the builders couldnt get the 6metre beam in so they cut in half and spliced with very similar plates to yours. That beam has a 30mm sag in it -which has caused them lots of issues, their own fault sonce they didnt level up the floor joists above....apparently large format bathroom tiles dont sit well if the floor isnt flat!
the sag isnt a point of weakness, but it does happen because there has to be some play in the fixings.
