Blended Whiteboard is a remote collaborative Mixed Reality (MR) system that combines physical whiteboards with virtual avatars to enable reconfigurable surface blending across distributed physical whiteboards. The system supports a unique collaboration style where users can sketch on their local whiteboards and reconfigure the blended space to facilitate transitions between loosely and tightly coupled work. Inspired by proxemics and the 3C collaboration model, Blended Whiteboard introduces three design principles: Dynamic F-formations, Dual-Mode Navigation, and Reversible Transitions. These principles allow users to switch between side-by-side and face-to-face formations, navigate the whiteboard in shared or individual control modes, and revert to real-world scale and distance between avatars. The system enables users to work independently or collaboratively, maintaining a balance between physicality and reconfigurability. The study compared different configurations of facing formations and navigation modes, finding that face-to-face formations were generally preferred for collaborative tasks. Canvas panning was found to be more efficient for shared tasks, while viewport panning allowed for individual control. The system also supports zooming and reconfiguring avatar relations to maintain a sense of physicality. The user study highlighted the challenges and benefits of balancing physicality and reconfigurability in remote collaboration. Blended Whiteboard provides a flexible framework for remote whiteboard collaboration, supporting both physical and reconfigurable use cases. The system demonstrates how the three design principles can combine physicality and reconfigurability in distributed MR whiteboards.Blended Whiteboard is a remote collaborative Mixed Reality (MR) system that combines physical whiteboards with virtual avatars to enable reconfigurable surface blending across distributed physical whiteboards. The system supports a unique collaboration style where users can sketch on their local whiteboards and reconfigure the blended space to facilitate transitions between loosely and tightly coupled work. Inspired by proxemics and the 3C collaboration model, Blended Whiteboard introduces three design principles: Dynamic F-formations, Dual-Mode Navigation, and Reversible Transitions. These principles allow users to switch between side-by-side and face-to-face formations, navigate the whiteboard in shared or individual control modes, and revert to real-world scale and distance between avatars. The system enables users to work independently or collaboratively, maintaining a balance between physicality and reconfigurability. The study compared different configurations of facing formations and navigation modes, finding that face-to-face formations were generally preferred for collaborative tasks. Canvas panning was found to be more efficient for shared tasks, while viewport panning allowed for individual control. The system also supports zooming and reconfiguring avatar relations to maintain a sense of physicality. The user study highlighted the challenges and benefits of balancing physicality and reconfigurability in remote collaboration. Blended Whiteboard provides a flexible framework for remote whiteboard collaboration, supporting both physical and reconfigurable use cases. The system demonstrates how the three design principles can combine physicality and reconfigurability in distributed MR whiteboards.