[Q] Low Disk Space warning from 10% to 5%

I hope this is the right section.

I own a Desire. I have a custom ROM ( JB ) and a sd-ext script ( mount2sd. Specifically, I mounted sd-ext/, which is 1gb, as data/ and data/ as sd-ext/. So now my data/ partition is on the sd-ext and all the apps are there ).

Now I have 100 MB free, and I get the low disk space warning, not allowing me to download and install more apps. I suppose this is because I have less than 10% of memory free, but my free memory is still as big as the original data/ folder, or some MB less.

Is there any way to lower the warning treshold to 5% so I won't be able to install apps when the free space will be 50 MB?

Many thanks