Do anyone know why some of the pictures just are shown as links and not as tumbnails?
You can make them appear as images by enclosing them in the img tag like I did below. I used the Img button to create the tags, but I think its an option after you do the upload). But you need to scale them down to make them fit. I think the max is 820 pixels wide.
You can use the Quote button to see what the post looks like:
How how long did it take to make the adapter?
For planning purposes maybe you should plan on 6s/6,000mah packs. If the 20,000 packs are good you will have some extra space. OTOH if they don't work out its something you need to do anyway.
Here's the link for the slipper clutches (Matt sells them with pulleys modified to work correctly). Scroll down to Friction Torque Limiters and Sprockets:
I don't think you can use them with a FW.