2. Handling: When fitted to the K-5 the combo feels well balanced - it becomes a fairly long lens but the extra barrel length is great for grab hold onto using your hand. Although I would probably still use a tripod.
The AFA1.7 was designed for manual lens and adds limited AF capability to them. If you use any AF lens, such as the 100WR with it, you loose majority of the Auto Focus capability. By that it means you have to Manual focus the adapted lens to 'roughly' the correct focus point, then, when hald pressing the shutter or AF button, the AFA1.7 will attempt to 'snap' to the actual AF point for you.
All macro focus lens have a long focus throw, and a probably better operated as manual anyway (I haven't used macro lens from Canon/ Nikon with USM so can't make comment on if they are better @ AF). Using the 100WR with AFA1.7 's AF assist feels quite awkward - you gotta manually throw the lens to roughly the right focus distance anyway. The AFA1.7 has a very limited AF distance window, and more than likely not it has some difficulty to lock on in such close focal distance as the operating range of a Macro.
I would suggest using this pair as a purely manual combo - leave the camera in MF mode and just manual focus using the macro lens. However, this does cause some confusion about the exact zoom ratio you will achieve with the 100WR in the end result.
An alternative is to leave the AF on, using the method described above to achieve rough focus lock, then manually adjust the lens for fine tuning. Almost like a primitive version of "QuickShift"