Engines,
Though the spaces designed have been generous, and to the requirement set, thank you for highlighting the classified part. There has been a hard challenge and significant expenditure of effort on getting the right compartments accredited to support Program-level data handling. Not to forget that other, non-F-35B aviation (and other nations' embarked F-35B), also need spaces to plan, brief, debrief too.
Pleased to report that all is well in the aftermath so we should be 'good to go' for First Of Class Flying Trials.