I am very happy with my modification of two pockets. My Arc Blast has several section hikes under its belt now, and there have been no issues with the pockets at all (or the pack in general). They work great, and pretty much exactly as I had imagined them to work if they were done right, which they were. I can organize my outer-pack gear easier, and having one mesh and one hybrid Cuben works very pragmatically. The bottom pocket has more exposure to abrasion from setting the pack down all the time, and the hybrid Cuben is more suited for this. The top mesh pocket is not as exposed, plus I can still use it to dry out gear like socks and gloves.
Though I am a bit obsessive when it comes to having little baggies and items, I should add. If you're one of those people that likes to just dump all your stuff into one big ditty bag, this mod is probably not for you. What usually goes in these two pockets are: tiny little stuff sack with my spare socks, my small ziplock FAK, small ziplock diddy bag, tiny stuff sack with my head net, 10m of rope neatly wrapped up, spoon, tent stakes in stake sack, head lamp, maps, and often one or two odds and ends find their way in there for each trip.
Still very contented with both packs, btw. In the future I am thinking about getting another very similar Zero to the one I have now, just so my wife can have a smaller and better pack for weekenders and such.
Another thing I should comment on is the space. For me 52 liters is more than enough than I need–plus the side straps and top/bottom straps also give you a lot of flexibility to put more gear/food if needed. On my last section hike, it was 3 days but I packed for 4 days of food (long story, check my last trip report). Fully loaded I could still roll the roll-top down 3 or 4 times. I'm pretty sure that I could stack two 8 liter dry bags full of food one on top of another, which for me would be about 10-12 days of food–and this of course includes my 3 season kit(s).
Hope this helps. Damn fine packs.