Michel,
As I mentioned in a previous post, clearly the price differential between Cuben Fiber and Silnylon is a big factor. Cuben Fiber is more than 3X the price of SilNylon per yard and because it's almost 20" narrower (48" Cuben vs. 65" Silnylon) it takes an additional %30 more yards of fabric.
For me the narrow width of the fabric is a major obstacle. I design pattern pieces to maximize the with of the fabric. So parts that designed to cut well on 65" width fabrics won't work. The product needs to be redesigned or the pattern pieces need to be cut up in a jigsaw of smaller pieces and additional seams. The extra seams means more labor for production and more potential problems in the field.
The third issue for Cuben Fiber is it's abrasion resistance. Used as a tarp or shelter it's strong and water tight, more so than with Silnylon. Used in conditions where abrasion is a factor, (packs, clothes, ground cloths, etc.) it does not perform very well.
Our first product to be offered in Cuben is the Refuge X. Simply because that shelter was designed with cuben in mind at the outset. As we get more comfortable in both the design and manufacture, we'll look at offering either cuben version of other products or new products all together.
Ron