How can the DPI setting be changed for the Logon Screen in Windows 8.1?

Microsoft has added per-user DPI settings. But this means that there is no adjustable DPI setting for the Lock/Logon screen.

You can change the DPI setting to be the same across all displays and this does affect the icons and font on the lock/logon screen. However, it does not affect any app/program that can run on the lock/logon screen.

Ex.
I use a 44" flat screen TV for my monitor on my desktop. Big enough for me to sit in my recliner and use my computer. I use the on-screen keyboard most of the time. (I don't want to keep a keyboard next to me.)

The problem is that with the new DPI setup the on-screen keyboard takes up nearly half the screen, which is too big.

I tried looking through the registry to see if I could find a setting for it. In the key HKEY_USERS\.DEFAULT\Control Panel\Desktop there is a string value named LogicalDPIOverride with a value of -1. I have a feeling this is where I can fix the issue. I tried changing the value to 0 and to 1 with no change in the result. Instead I noticed that after logging out and back in the -1 value was back in the registry.

How can I change this default DPI? Can I use the LogPixels string that worked for DPI in Windows 7?

Here are two Screen shots, one of the Lock Screen and one of the Logon Screen: