Engineering the Perfect Duct

Alright, here's the situation:
I'm building a sweet box from the ground up for college. It's going to be in a Dragon case. I've got an SK-7, 5 92mm high speed panaflo's and some thermoformable plastic in the mail as we speak.
Originally my plan was to have a panaflo on the heatsink and a matching panaflo in the back of the case with an airtight plastic duct connecting them. However, after reading a bazillion posts, I decided that it would be more beneficial to first have an airtight riser that would keep the fan 25mm or so from the heatsink, thus reducing the dead spot, then from there have a duct that was connected to a hole in the back of the case. I came up with this design based upon several of nerdlogic's posts that state that a straight on shroud is beneficial and on various other posts that stated that a second fan at the end of the duct wasn't beneficial.

However, I've recently read several posts where adding a second fan to the duct helped reduce temps, so, with a few days left before my materials get here, it's time to come up with a final design.

At this point I'm still planning to go with the 25mm shroud + a duct to a blowhole in the back of the case. I could then attach an extra fan to the back of the case and have it blowing into the duct to see if this actually did help temps.

What are your thoughts/suggestions? I got some cool transparent red plastic so this thing should look pretty sweet, but I'd like it to work well too.

I just posted about the exact same thing. I reckon that as long as the duct is long enough the fan on the end should make the air getting to the second fan slightly faster and so the second fan is doing less work. Is a theory anyway. I think Im going to give it a bash but with not quite the same quality materials (ie a coke bottle and some a cheapass stock fan. that said though I will have 2 fans both of different quality which means I will have to decide which one will go where, or maybe Ill just have the one decent one ducted above the sink and a hole in the case. Whatever let us know how yours goes it should be interesting if not helpful.

I know you said you had a 92mm fan, but I was thinking of using a 3 inch diameter clear plastic mailing tube for a duct from my window to the 80 mm cpu fan. I've never tried it. It was just something I've been kicking around in my brain. You might be able to find a 3 1/2 inch mailing tube in a stationary store to fit your fan.

What if it rained? You would be up a creek then. wouldnt you eh eh eh eh?

Are you buying a shroud for your heatsink to raise your fan 25mm, or are you making one, and if you are making it, what are you using? I want to do the same thing with my Volcano 6.

(I saw some for sale online and I also saw some that will take a larger fan than the 60mm on the heatsink already. Would it be beneficial to use a larger fan? I don't want to make my system any louder.)

You're right ,Bigdogbmx, hehe. I should have clarified. I meant the window of my case, not outside window. Thank you for bringing that to my attention.

ooops I should have worked that one out.

Well, assuming that it actually works, I will be using some FIMO plastic modeling "clay" It's basically a moldable plastic that you solidify by curing in the oven.
So I will mold it until I have the correct size and shape for my shroud/duct and then I'll pop her in the oven for 30 minutes and voila, instant, professional looking duct (i hope)