Huh...I've never had the valve pull down on the material at all, BUT...the DUI 450 is quite a bit more stiff than the DUI 350 so you know the deal: your mileage may vary! 
As noted, I'm really happy with the unit, I've not yanked it apart since I installed it and aside from running either vinegar or fresh water through it after each dive I've not done any other maintenance. The thing is amazing...it simply works.
On the weezle issue, I'm in the process of replacing it. It works great - the last time I used it was a dive on the St. Augustine, which is a 250' dive off Ocean City, MD (with Ted Green, OC Diver, whom I strongly recommend), and while it was a long cold dive I was comfortable during the entire run. But I am mindful of your adventure, Eric, and it clearly requires more loft/weight than the reflective/thinsulate options, so I'm going to replace it here shortly now that I'm back in the PNW. On the east coast I seldom needed that much thermal insulation, I generally wore fleece, but the water is colder in Puget Sound and points north. Best to both you guys in your deliberations...
Doc
As noted, I'm really happy with the unit, I've not yanked it apart since I installed it and aside from running either vinegar or fresh water through it after each dive I've not done any other maintenance. The thing is amazing...it simply works.On the weezle issue, I'm in the process of replacing it. It works great - the last time I used it was a dive on the St. Augustine, which is a 250' dive off Ocean City, MD (with Ted Green, OC Diver, whom I strongly recommend), and while it was a long cold dive I was comfortable during the entire run. But I am mindful of your adventure, Eric, and it clearly requires more loft/weight than the reflective/thinsulate options, so I'm going to replace it here shortly now that I'm back in the PNW. On the east coast I seldom needed that much thermal insulation, I generally wore fleece, but the water is colder in Puget Sound and points north. Best to both you guys in your deliberations...
Doc
