What CUBEN FIBER did you use, not the weight but the CUBIC TECH trade name?
I used ct2k.08 (.74oz, MLD's .6) and made a mid a little longer, but shorter and narrower than yours. I used sil for the tie-out reinforcements and 1.9 for the peak and a #zipper. All are as light or lighter than you used but my weight was 8oz, however i did add line-locs to the 6 tie-outs, so subtract 1 ounce, but still heavier.
I am thinking you may have the one step lighter CUBEN fabric.