Wall/Wheel Clearance

I know this has been discussed before but I would like some input on the distance between side wall and wheel. Right now I have approx 3/4 inch between the two. This is my finished space. I remember MJ saying something akin to being able to put your fingers down to the second knuckle was a safe measurement. Well I can do that and more. There shouldn't be any flexing at the top of the tire should there? Is this space going to work for me or should I use a spacer? If so where are they available? I have a HF frame with the 4 lug 12" tires.
Thanks Philip
Thanks Philip