Joining flex duct together

[oscargate]

I was going through the cooling threads and most people are using the ~10" flex duct for miners.  I was thinking I may have ~10 x 10" flex ducts dump into a bigger metal duct (24"?) that would run about 10' to a window with a 3500 CFM window fan. 

I wasn't sure if anyone had joined together the 10" ducts or whether people just run all 10 separately to a window?

My garage is setup like this

 ___________________________
 |           --miner shelf--               |
 |                                               || window -- fan (3500 cfm exhaust)
 |                                               |
 |                                               || window -- fan (3500 cfm intake)
 |                                               |
 |______garage door closed_____|

Temps are about 85F with all my mining gear going full blast (without the ducting) and outside ambient temp is about ~65 F... Goal is to get temps down below 80F