I think I've found something, but needs someone verify it:

If you:

1. Go to any one of the Device Configuration pages, save the page locally, and edit save the file (see ZoSo's last post).
2. Go to any one of the Device Configuration pages EXCEPT the one in Step 1.
3. Open the local file edited and saved in Step 1 (Note: not sure if it has to be opened within the same window/tab/session), choose a "customized" profile and save.
4. Result: it seems that it changes the config for the device mentioned in Step 2 instead of the one in Step 1 (no need to change the device ID and name in that local file).

If this really works, then we just need one local file to modify all of the devices

Okay, great, have bolted on a draft paragraph to the existing Profiles FAQ, with link to Moonian's step by step found in post below (Credit given).

http://www.worldcommunitygrid.org/forums/wcg/printpost?post=135867

It's not a secret, but not going to advertise it either until it proofs ruggid and not causing upset in the Mondo BOINC :D

OK, here you are:

Step 1: Create a customized profile
1.1 The URL of the page configuring a profile is something like this:

where YOUR_PROFILE_NAME is a profile name of your own choice.
1.2 Open the page using the above URL, config the settings as if it is a normal profile, and then click .

http://imageshack.us/photo/my-images/10/54106074.png/

1.3 If successful, the new profile should list under "Profile Name" of the Device Manager-->Device Profiles page.
http://imageshack.us/photo/my-images/406/45652452.png/

=============================================

Step 2: Apply the customized profile to a device
2.1 In the Device Manager page, click the link of the device you would like to use the customized profile you have just created. This should open a Device Configuration page.
2.2 Save that Device Configuration as an HTML file to your local machine.
2.3 Open it with a text editor (e.g. Notepad).
2.4 In the file, there should be a section that looks something like this (in IE7):

or this (in IE8 and Firefox):

This is dropdown box containing the profile names.
2.5 Add the option for the customized profile you have created in Step 1. The block of code should become something like this (in IE7):

or this (in IE8 and Firefox):

where YOUR_PROFILE_NAME is the profile name you have created in Step 1.
2.6 Somewhere above the block of code mentioned in 2.4-2.5, there should be a section that looks something like this (in IE7):

or this (in IE8 and Firefox):

This is for the link for the button in the page.
2.7 Add the string http://www.worldcommunitygrid.org just after action= (in IE7) or action=" (in IE8 and Firefox) so that it becomes (in IE7):

or (in IE8 and Firefox):

2.8 Save the file and exit the editor.
2.9 Open the file with your favourite browser. (Note: as scripts run in a local file, your browser may block them from running. Allow them to run temporarily if they are blocked.)
2.10 The dropdown box in the page should contain the customized profile you have created in Step 1. Choose it and click .
http://imageshack.us/photo/my-images/407/210zi.png/
2.11 Go to the Device Manager page and see if the device's profile has been changed to your customized one.
http://imageshack.us/photo/my-images/215/211c.png/
You may also click the Update button of the BOINC Manager for the said device to check if it changes to use the customized profile.

Edit: Added Firefox code

Edit 2: Added some screenshots too

Edit 3: Fixed something

You're welcome downtowndan

As for the slight difference in the code... I'm not sure if it's something related to the choice of browser (I used IE8 to save the page)

Thanks Sekerob . I've added the code for Firefox (don't have browsers with other engines though, so dunno what the code looks like in them) and highlight stuffs need to be added to the file (edit: just added some screenshots too). Please drop me a note if there's anything else I've missed :)