You Shot HD, You should Edit HD.
Now, those stills seem small. Can you get originals?
Can you resize?
If the stills need to be the best with the current size, I might edit in a SD sequence. DV NTSC Easy setup.
If you do this, when the edit is locked, change the sequence to 10 bit Uncompressed and re render all and then export using “Current settings”.
Take that file into compressor to create your deliverables.
BUT, My first choice would be to edit in a 720p sequence. Drop the 1080 in there and get larger stills. Make sure all the Frame Rates Match!
Chris Tompkins
Video Atlanta LLC