It won't be that much of a floater
A typical 800 sq in pattern plane from say-1990 weighed 8 lbs -done right -Ibuilt lots n lots of em and customers also did the same
They land at say 30 mph.
a 45 glow engine will fly that setup
or a 90 four stroke also is a good nice cruise setup
Here is the bottom line
It is physically impossible for you to make this setup too light.
ideally it would weigh 5-6 lbs at that size for really docile flying. as a newcomer to all this you will likely overbuild the model so be careful! That extra weigh all goes into making the plane more sensitive to speed and flying angles

You just can't beat lightweight for getting the best results
the airfoil use should be based on what will build into a strong structure The actual airfoil number means little. go for an average of about 12-14% thickness
Take a look at the old Seniorita kits by SIG - this structure is good for a 800sq in model and all up flying weight is 4-5 pounds.