Hi Clare,
To turn off borders from float bars you must first exclude the float bar borders from the applied style sheet, and then set this border to 0. The steps are:
1. From chart area/Appearance settings uncheck "Outline Data Points"
2. Data, Value groupings editor go to Appearance/Border. When the border style dialog appears, uncheck "Use Automatic" and specify border width.
Best Regards,
Nevron Support Team