How would i make an exhaust fanduct for pal8045?

I was thinking of making a funnel so to speak out of cardboard from the top of the fan (highspeed 50cfm sunon), to the exhaust fan on the side of my lianli pc68 (i have an exhaust blowhole fan at top though for case). Now i have a few questions about this before i try to make it.
1) should i use the ehaust fan on the side of the case since it is less than 50cfm? or should i just take out the fan and use the open hole so all of the air would be able to go out?
2) if i put some acoustic sound dampening foam in the duct (or some carpeting, or anything that makes the noise more bearable, will this duct still work as well? also, will it get rid of some of the noise?

The easy way is to get the tubing used for exhausting the steam from a washer/dryer. Slip one end over the Alpha fan (set to suck of course) then the other end over the exhaust fan. It's best in my experience to match the two fans. I am doing this with my Alpha 8045 and it cost me peanuts to do. My case temps are nice and low too.