dyneema or silnylon for a roll top lid in my ion? grossgrain?

I'd go with the silnylon. If you're going to sew a pocket on the back I'd recommend that you add grossgrain loops for a bungee system over the pocket. This gives you a lightweight way to hold wet tarps, rain jackets, etc.

I'd go with Dyneema if cost was not an object. I often scrape the top of my pack against overhanging branches and when crawling under downed trees. I'd be worried about ripping up silnylon and I don't like to worry about such things. On the other hand if I already had the fabric…

The grosgrain from joann's is the same stuff that the cottage makers use so no need for a special order. It is thin but it's more than tough enough for most uses.

well I have some elastic cord and micro cord locks laying around also… I've thought about doing a cord system on the back to strap things to and to cinch the pack semi tight to stabilize small loads, but couldn't decide… I paid $30 to get my 2008 ion shipped to my door. so essentially I got about $30 left in the planned budget for making my ultimate lightweight pack. I just couldn't justify the $160 for a MLD Prophet either, when i could cheaply and quickly fab it into an ion. I guess i might as well put in a cord system while I'm in there.

I have to make an order from qwest outfitters anyhow for some lycra stretch mesh for the side water bottle pockets. I'll be using my Jam2 hydration sleeve for the back stretch mesh pocket. But in order to get dyneema I'd have to go through thru-hiker also, which means shipping x2… hmmm… decisions, decisions… That's always the hard part.