Insulated ducting - running 4 inch reg duct through 6 inch insulated?

I have 2 1000w vented hoods, 6 inch. My carbon filter and blower is 4 inch so I have reducers(?) on each end of both my lights. I need to drop about 10 degrees, so I picked up 6 inch insulated ducting.

2 questions

1) If i replace my existing ducting with the insulated ducting (4 inch to 6 inch) is there going to be any problem since my blower and carbon filter is 4 inch? Seems like id lose some push in my mind.

2) Is there any issue with just running my existing 4 inch ducting through the 6 inch insulated ducting? This would make it easier to work with, since the existing ducting will hold a shape far better, and I wouldnt have to worry so much about "sharp turns" in the ducting. The only thing that keeps me from this is that I think hot air leaking from the 4 inch duct would just be chilling in the insulated duct, which would not have much airflow itself (all the air would be going thru the 4 inch duct inside the insulated duct.


thoughts?

sounds like it would be fine to me. Does the 4" leak alot?

some people say no, but those people are full of shit. You can feel the heat coming off of them just like you can feel heat coming off your ballast. Anything hot is going to emit heat, especially since it isnt specifically insulated.

I missed something? are you saying the 4" gives off heat whan your running it? so you want to put the 6" around it?
If your 6" goes out of the room just make sure it higher. heat rises so what ever heat would just flow to the highest point og the 6".