How can I delete event files from iMovie to save disk space?

I have been shooting a lot of HD video of my son's soccer games and am now realizing some of the problems with the newer iMovie 10. It appears to not allow for partial video deletion of videos in events (really too bad because previous versions of iMovie did this really well), And, sometimes it will not actually move the deleted file to the Trash to help free up disk space on the computer. This is also a problem because I have to did around in the View in Finder mode to find the events I just deleted in order to move them to the Trash manually. Yeegads! All of this said, what I appear to have happening is a huge amount of video that I never plan to keep (most of a 90 minute soccer game does not make it into highlights -- imagine that?) clogging up my hard drive. My poor computer needs to have a cholesteral check.

Any advice on how to manage large video files 40 minute HD files within (or outside) of iMovie 10 so that I can efficiently eliminate irrelevant content and actually delete files to prevent disk overload would be greatly appreciated. I am thinking about using iMovie 9 to edit down and delete the unwanted footage and then update the files into iMovie 10 for some of its bells and whistles any problems with that?

I must admit, I think iMovie 10 is a failure in certain essential ways. It dropped Keywords, its deletion is not true deletion, and it's all or nothing when deleting an event. I have always been a huge Apple fan, but this new release of iMovie 10 has not been a good user experience for me. I have read a lot of feedback from others with similar problems and issues with iMovie 10 and would really like to understand what Apple plans to do to address some of these defficiencies in what will hopefully be a much better next version.

Thanks for any help you can provide.