Hi Mark,
Stick the simplest pattern and method!
Here's mine.. just a simple strap riveted through the shield board before the linen covering went on.
http://i20.photobucket.com/albums/b242/ ... hewall.jpg
and how it works.. From a brief report after marching 70 miles of Hadrians wall with it..
The method I employed for marching with a clipeus proved to be incredibly comfortable and practical for this type of shield. It can also be easily swapped from shoulder to shoulder, to ease tiredness – even whilst marching, without difficulty. The simple design also allows both hands to be free to carry other items.
The strap crossed the chest diagonally at the mid-sternum, thus making it possible to restrain the helmet (attached around the neck) to the chest preventing any movement.
If needed the helmet could be arranged so that the weight was supported entirely by the shield strap, taking away the strain on the neck. The act of arranging the strap over the helmet shortened the strap by some 150mm, allowing for a higher placement on the back, thus restricting the movement of the shield whilst marching. It also works well when hanging a shield from a horned saddle.
Construction
Basically, the strap is 1.25 metres long by 40mm wide by 3mm thick vegetable-tanned leather, secured to the shield at both ends via 4 small rivets. (Two each end).
The strap is secured at points as per the diagram below.
http://i20.photobucket.com/albums/b242/ ... dstrap.jpg