Judging by the specs on the Da-Lite web site, it looks like you could suspend the Cosmo from the ceiling. I would think you could just use a chain and s-hook combination to adjust the height of the screen.
Eyehook/chain method is the default Da-Lite ceiling mount method. It should describe how to do it in the installation instructions. It does in the installation instructions PDF on the Da-Lite web site.
Alternatively, you can buy optional "Floating Mounting Brackets" from Da-Lite that are designed to let you slide the screen left and right after mounting; the screen slides along the mounting brackets. I bought these brackets because of my low 7 foot ceiling. I can hang the screen closer to the ceiling with the mounting brackets than I can with the eyehook/chain method.
Call Da-Lite and they will fax you a side-view/measurements picture of the Floating Mounting Brackets.
I also purchased the same screen last month and ceiling mounted it. It is suspended from the ceiling but I used aluminum ceiling mounted curtain/drapery tracks about 18" long on each side of the screen. Each segment of curtain tracks are attached to the ceiling joists with four 3" lag screws for added strength and distribution of the 100+ lbs. weight. With this setup I can laterally adjust the screen just in case my center of lens measurements were slightly off target and of course the height of the screen can be adjusted by varying the chain length. The only direction I can't adjust is the forward and back movement of the screen. Works very well because of the adjustability.