After rereading your post, I am not sure if the rims will work w/a 4.75 BS, the most you can usually run is 4"BS on an IFS. Youwont know if they work until you mount the front tires.
I thought 17s would be get me more clearance when I air down.
The 17's will give you more clearance when aired down, but will reduce the size of the contact patch the tire makes when aired down. The type of tire will also determine the size of the contact patch, i.e., a more pliable sidewall will flatten out more, a stiffer one not so much. It is likely that w/the Baja's on 17's, the contact patch wont be much larger than stock 28 tires. Of course if the BS works, you could live with the smaller contact patch until you lift it and run larger tires.