Windows 7: changing Auto Full Backup Settings in Registry

My PC creates new full backups far too often for my liking. After digging around I found this disucssion on the subject that revealed that you can change the defaults for whne this new full backup is created by editing the registry. It's way down near the bottom

Windows7 Backup not doing incremental


the critical bit is this

We have introduced automatic full backup feature in Windows7 to help customers who run into a situation where they never create full backups. When their backup target eventually gets filled, they are left with only one backup set to delete. They need to delete the entire backup set to resume backups and so end up in a situation where they do not have any backup.

The rules that determine when to take automatic full backup are:
1. If previous full backup was taken 1 year back
2. Ratio of size of deleted files + older versions of files in current backup set is 50% or more of the size of the current backup if it were full.

We deliberately did not allow forcibly starting new backup set or configuring these rules through our UI because we did not want to confuse users about full backups, incremental backups, automatic full backups.

If you find that these settings do not match your requirements, we allow the defaults to be tweaked using registry keys.



Registry key to control enable/disable automatic switching to full backup:
Path: SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsBackup\AutomaticFullBackup
Name: Enabled
Type: DWORD
Value: 0 indicates automatic full backup is disabled, non-zero indicates it is enabled
Default if not specified: 1
Registry key to control the time period when backup should automatically switch to full:
Path: SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsBackup\AutomaticFullBackup
Name: TimePeriodInDays
Type: DWORD
Value: Count of days
Default if not specified: 365
Registry key to control the % of deleted/missing + older versions of files that determines whether to switch to full backup:
Path: SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsBackup\AutomaticFullBackup
Name: OlderFilesSizePercentage
Type: DWORD
Value: Percentage value from 0 to 100
Default if not specified: 50

I thought I would try changing the default for the % deleted files to 75%. After digging in the registry I found this path only under HKEY_LOCAL_MACHINE, but the keys mentioned above don't seem to exist? So my question is could they be hidden in someway? i can't understand how they can't be there so don't want to create them. Coudl the discussion I found refer to the pre-lease version and therefore i am looking at the wrong thing and the controls on the backup have moved?

Thanks for any advice

Mike