The call to *winpnl is designed to save/recall window sizes for Nomads -- the graphical environment -- which is what we assumed since you are running WindX.
For Text mode the issue is the PxPlus container which when PxPlus first came out was intended to be a container for your windows thus its size is controlled by the user, however the following logic can be used to adjust it.
read data from fin(0,"XYPOS"),sep="," to X,Y,WD,HI
read data from fin(0,"XYCLIENT"),sep="," to CHILDWD,CHILDHI
Now those value +16 and +110 are somewhat arbitrary but work for Windows 10 which includes the shadow of the window in the actual window size. There is an API call you can use to get the exact value but for simplicity I would use these.
Put this code in the start of your application and the system should set the outer window frame to match the inner frame and its font size.