I don't think that action is configurable... again, it's been suggested. Ideally, people should be able to configure dblclick on empty white space to perform any command(s) they might like. I'd REALLY like it to be configurable based on SHIFT|CTRL|ALT dblclick actions as well.
BTW, that should only happen in List/Icons/Thumbnails mode. In Details and Power modes, doube-clicking an empty space in the file list should have no effect.
While the die-hard ".." fans will not be any better pleased... those looking for 'quick' ways of getting to the parent dir might be pleased with the following feature addition to opus v9.0.0.7:
I'm pretty stoked about it... and in just a day so far, it's become a 'muscle memory' item for me that I've done at least 50 times today so far... Jon and Greg RULE!