One thing you might try is to use a junction point. I have found them incredibly useful in situations where I have a small primary drive and a large secondary drive.
Rather that instruct your installation programs to install to your "D:" drive or whatever (some applications don't give you the option or may not operate properly if you so), create a junction point in place of the applications default installation directory
and point it to your second drive.
Here's an example:
Office 2010 wants to install by default to "C:\Program Files(x86)\Microsoft Office"
Using the following command from an elevated command prompt...
mklink /j "C:\Program Files(x86)\Microsoft Office" "D:\Junction Point Targets\Applications\Microsoft Office"
...will result in any files sent to "C:\Program Files(x86)\Microsoft Office" actually being redirected transparently to "D:\Junction Point Targets\Applications\Microsoft Office"
Although I haven't tried it, the same most likely can be applied to "MSOcache"
There are a small number of folders that cannot be redirected through junction points, but they tend to be special system folders, like the Windows SxS folder. Most everything else I have tried works flawlessly.
I currently have, in effect, 179GB of programs installed on an 80GB SSD, with 52GB free, all because of junction points.