A quick update, I wound up getting an Infocus IN3128HD instead of the Optoma, the deal was just too good to pass up. First of all, the IN3128HD has a max focus that natively will support a 300" WIDE image, all of the other projectors only support a 300" DIAGONAL image, this was key because my image is going to be 290" wide, just inside the specs.
After it arrived, I started testing different settings, what I found is that it can focus perfectly as far away as I want it to, I wasn't about to try outside due to it being -10F right now but I tried it at the longest throw I can in my house, 48' (nearly 500" diagonal!) and I hadn't even maxxed the focus ring, it could still rotate further.
What is also interesting is that on the other side, I could focus the image MUCH smaller than the specs indicated, according to the specs, the smallest image I can get is about 40" diag, in reality, I was about to keep moving it forward and on the nearest focus setting, it was down to about an 11" diag image, MUCH smaller.
I find all this very interesting since I am used to manufacturers fudging specs in their favor, you would think that if they were going to go to the trouble of specifying focus distances and image sizes, they would at least state what their products can do, not far less.