To resolve this issue you may have to put the chair model in the default input slot instead of the X-Evenly. You can then control the spacing between chairs using left/right padding. To get the chairs to go around the corners set the Y-mode to free, this will calculate the length or each row individually. Finally if you want to avoid slicing the chairs in the corners, set the X-Bevel mode to None. The only slight issue with this technique is that you'll get some slightly wobbly chairs right in the 90 degree corners and the chairs will no longer be aligned in columns.
Hope that helps,