andykub
I would like to keep as much as possible off my system drive
Don't we all.
Sometimes you can choose, sometimes you can't. Sometimes you can move things after the fact and edit the registry (but then have to redo it after the next update), sometimes you can't. Or you can set up symbolic links so Sonar will be fooled into thinking things are where they should be when they're not, and this'll survive an update.
This last option is probably the best, but I don't do it (yet) because my main system folders are already sym linked (that's how Windows does different languages) and don't want everything to go through chains of links (maybe that's not a problem ?). Here's
a post describing how.