Associate 64-bit IE8 with Internet Shortcuts

I decide to try the 64-bit IE8 for a while since a 64-bit preview release of Adobe Flash Player is available now. So, I opened regedit.exe (Windows 7 x64) and manually changed the associated 32-bit IE8 to 64-bit IE8 for related file extensions (htm, mht, etc) and protocols (http, https and ftp).

Edit: I did this manually, because things didn't change after the 64-bit IE8 had been selected for file extensions and protocols from "Default Programs > Associate a file type or protocol with a program". Also, every file extension listed under "Set your default programs > Internet Explorer > Choose defaults for this program" is by default selected and cannot be de-selected.

The manual work was pretty easy because the only thing I should do is editing the registry value that points to the location of the 32-bit IE8 and removing the (x86) from "Program Files (x86)".

Edit: That's useless, too. I found out that later.

But, how should I change the registry value for Internet Shortcut, i.e., the .url file extention?
The "Default" value stored under "HKEY_CLASSES_ROOT\InternetShortcut\shell\Open\Command" is

"C:\Windows\System32\rundll32.exe" "C:\Windows\System32\ieframe.dll",OpenURL %l

That value activates the 32-bit IE8. What should I change it to?

I've managed to get full controll over this key and tried editing the above registry value so that it is changed to point to the location of the 64-bit IE8, as follows:

"C:\Program Files\Internet Explorer\iexplore.exe" -nohome

But that's no good. It's still the 32-bit IE8 that opens Internet Shortcuts.

Edit: After all, is it possible to set the 64-bit IE8 to be the default browser?