Complex sentence: After successful trials the new system was upgraded further so all the benifits were kept without the need the fold the nacelles and incorperated into all later Federation Starships including the Sovereign-class.
Split into simpler sentences: After successful trials the new system was upgraded further so all the benifits were kept without the need the'fold' the nacelles. This upgrade was then incorperated into all later Federation Starships including the Sovereign-class.