Use 1/2 carbide end mill(.250 radius), predrill .500 or bigger(better) hole for clearance at X0.Y0.If step .300 is too much change J0.3 to J.15.
It is not machine proven program so be carefull running it.
hope it helps.
Subroutine O502 can be changed to cut different shapes nad sizes.
I believe , you have to use Radius Geometry offset of .250 for tool # 1.
Copy and paste program below and you are all set
(X0Y0 CENTER OF THE POCKET)
(Z0 TOP OF THE PART)
G150 P502 G41 D1 Z-.25 R0.05 J.3 K.01 F10.
O502(POCKET 4 X 4)