The real problem with an offset flange is not that it clogs up, but they brake often. Most of the time people assume they are as strong as a regular flange and tighten up the toilet, without realizing they will break.
But If you are only nine and one half inches from the wall, I would use a ten inch rough toilet. You can buy them special order from Kohler or American standard. Once you get the toilet, set the bolts 1/2 inch forward of the center line. I have done this with no problems. Since the actual opening of the base of the toilet is only two and one eighth, and the opening of the flange is typically 3 or 4 inch, your toilet will still flush directly down the drain. You can use the standard bowl wax without the horn. This saves breaking up the floor and installing an offset closet flange.