Tubus Swing
http://www.tubus.com/product.php?xn=65 as a front rack for a Suspension fork MTB,
is going to allow the suspension to work better, as It adds no weight to the unsprung lower part.
The load is going to be carried by the 5mm bolt , the QR running through the hub..
What is that a rear skewer to be long enough?
I was thinking that a hard rubber or plastic spacer here to ensure that pressure is being applied to the dropout would be sufficient. What do you think?
I wouldn't ride that.. [particularly off the road] if you must use spacers make them Metal ..
so you can get the skewer tight enough..
Generally, Light, newer external cam QR's are not as powerful as the internal cam type ..