The survey won't help you. Look up adverse possession laws for Florida using Google. Basically, if someone uses your property for a period of time, without your permission, they can claim it as their own. By moving your fence eight feet back from the line, you are giving him an open invitation to do just that.
It will take some years, five I think in the case of Florida, but he will be able to do it if you don't take precautions. The fence placement will not look good to a judge, and you will hard pressed to defend against an adverse possession suit if your neighbor decides he wants the land.
All he has to do is use it for the specified time without your permission, and you have lost it. The use can be as little as mowing it, in some cases. One way to short circuit adverse possesion is to give the other person permission in a provable manner. Other than that, you have to keep him off of it, which is hard to do if the fence is eight feet on your side of the property line.
You really need to educate yourself on this stuff if you plan to move that fence back. You are at risk.
I'm not an attorney, so don't just take my word for it. Consult other sources, preferably a real estate attorney.