So let me get this right to be save you need a 5x5 field as a center (since 3x3 is a risk and 4x4 doesnt have a center).
P = pavement
T = Tree
PPPPPPPPPP
PPTPPPPTPP
PPPPPPPPPP
or
PPPPPPPPP
PPTPPPTPP
PPPPPPPPP
What would be the best option and still be safe?