Slimline Question

I was scheduled for installation today after a few screw ups that would take too long to post. Current set up is an old dual lnb mounted on a tripod on the roof to point the dish above trees in the back yard. I was hoping that the installer could find a site on the roof for the AT9. Not possible according to the installer. He advised me to wait until the slimline was available in this area (about a month). He said he would be able to swap the slimline and the old dual lnb dish and keep the slimline mounted on the tripod, just like the old dual lnb dish.

Is this possible? From what I've read here, the slimline is only slightly smaller and lighter, and mounting on a tripod above the roof line might not work. Any advice would be appreciated. I've been trying to get the HR20 for over a month now, and would prefer not to wait another month just to find out it is a hopeless cause.

Thanks in advance.