1.) Could not say ...but I'll be having a front baffle around 5cm -10cm wider soon because I cocked my dragonfly up. (Listening to the Prometheus the wider baffle gave a slightly warmer more upfront soundstage, whereas the standard baffle width was more "accurate"..
2.) The footplate I think is just ornamental...the opening of the horn to whatever it hits..ie. floor or footplate should be 10cm. I did mine with 18mm round wooden pegs..but it turned up crooked.(holes not drilled straight)....My idea would be to simple cut the wood 10cm longer and cut out a hole so you end up with wooden feet...if you know what I mean... (Maybe Robert has tried this before and can comment...I'm just going ahead with it...regardless :-)
3.) Contrary to the idea the photo's give you..the drivers should be fitted to the front of the front baffle...4.)so no hatch is necessary. And the edge of the speaker aperture needs not be rounded..
5.) Don't know.
Best of luck Brian!
To infinity and beyond!!!