I recorded a screencast of a "how to use this software" tutorial. I imported the .avi files into Kdenlive. Now I want to add Libre Office Impress slides for part of the narration. I have three questions

1. Working with Slide Clips
When I import one slide clip at a time I must choose "Frame Duration" at the time of import. If I set "Frame Duration" to 5 seconds, can I later change how long the slide shows?

Is below the correct way to do it?
To make it longer:
To make a 5 second slide a 7 second slide do I just make a cut after 3 seconds and duplicate the last 2 seconds.

To make it shorter:
To make a 5 second slide a 3 second slide do I just
make a cut after 3 seconds and delete the last 2 seconds.

2. Six Slide Clips become One long clip
I imported six slides and set the "Frame Duration" to 5 seconds. I ended up with one clip of 30 seconds which I had to then cut up with the razor tool into 6 separate clips. How do I import the slides so that they remain 6 separate slide clips?

3. Best way to export out of LO Impress
- I can export one slide at a time as a .png file. That allows me to choose frame size and resolution
- But if I try to export the whole presentation as HTML (to do all the slides in one shot) I don't get that choose frame size dialog.
- Can I export all the slides in one shot in a way that lets me choose frame size so that I don't end up with columns or letter boxes? (Sorry for the Impress question in the Kdenlive forum)