If I right click a 7z file, I can go to 7zip->open archive. I was wondering how to set this action to the double click/open? I would like this solution in a fashion that could be used in an unattended fashion, of course. Thanks in advance for help

Run the 7zFM, go to the settings, "plugins" tab, click "configure" and check the extensions you want to associate. There's also the commands presented in the context menu and other options.

You only need to backup the settings. the easiest way is by using .reg files
First, configure all 7-zip options as you want (in the settings dialog, in the "add files to archive" dialog for each archive type, the colums sizes for each archive type, etc...).
Then, open regedit and export the "HKLM\Software\7-Zip" key (it contains the main settings).
Then, export the associations. Those are in HKCR, and there's 2 keys for each :
If you associate 7-Zip with 7z archives, the keys are "HKCR\.7z" and "HKCR\7-Zip.7z".
If you associate 7-Zip with Zip archives, the keys are "HKCR\.zip" and "HKCR\7-Zip.zip".
If you associate 7-Zip with cab archives, the keys are "HKCR\.cab" and "HKCR\7-Zip.cab".
... and so on.
(note that "associations" are the ones checked in the settings and concern the "double-click". 7-zip will always display the "7zip->open archive" submenu for each recognized archive)

You'll get a lot of .reg files, put them into a single one. To reinstall the settings, import it right after 7-zip install.

final note : all of this will not work if you change the install location (you'll need to change all the pathes in the .reg)

thanks I used regshot to do compare.