I like to copy the BPAV Files from my SXS cards to a DVD or hard drive for storage. Most of the time I have small portions of the clips that are worth keeping.
Does EX Clip Browser have the ability to trim the original clips? If it does, I can't figure out how to do it.
I believe that if you want to archive the actual BPAV files then you can't mess around with them in any way. However, there is nothing to stop you selecting sections of clips within EX Transfer and then putting them on your archive drive but I imagine that you have to first import into your system, choose a codec and then export the files. Others will doubtless suggest the best route.
You can trim and/or delete clips in Clip Browser and then save and burn the revised BPAV. I do it all the time to save disc space. Just set in and out points on the clip, select "Edit/New clip using in In/Out selection" and delete the original clip.