The supporter plugin appears to override any space limit quota I set for non-supporter blogs by giving those blogs the same space quota set for supporter blogs.
For example, if
the Site upload space box is checked to Limit total size of files uploaded to 25 MB from my normal WordPress setup tab, then it gets converted to whatever value I put in the Quota Increase field on the settings tab for Supporter. Not good!
System specs: WordPress 3.1.1, BuddyPress 1.2.8.