For the technical climbers in the club... here is an interesting article about a potentially very serious problem with lowering a climber (from a top-belay) while using an ATC-Guide in auto-block mode... http://www.rockandice.com/climbing-accidents/climber-dropped-when-lowered-in-autoblock-mode

I found it beneficial to watch the instructional video (link found on the Black Diamond site) for how to properly use the Black Diamond ATC-Guide device... especially how to use it for lowering a climber... https://player.vimeo.com/video/22320202

This shows again, that simpler is most often safer than exotic. Belaying the second off top anchor on a munter will use much less gear and space: munter needs only one carabiner (as an exercise try to count how much gear you will need to use ATC-guide), is much simpler to inspect and 100% safe - it will lock at any angle. On multi-pitch alpine routes rigging and cleaning such complex systems with autoblock takes a lot of precious time too. Also, munter will let you control the shock force - experienced climbers never break the fall abruptly - a shock can overload the anchor, better let the rope go smoothly a bit, increasing friction, until it stops. If belay is swapping, no extra efforts are needed - the second will just pass the anchor, when autoblock will have to be taken down - eating expensive time. Add non-zero probability you can drop belay device in the process, so..