Yeah this script is around here on the forums in other threads and depending on the version of Higan it may or may not work.
For example 1.01 requires this script but 1.02 does not, all you need is the command line parameter --fullscreen. I have no idea what 1.03 requires since I have't tried it out, Byuu is known to change tiny things like this up on a whim.
#NoEnv
Sleep, 3000
SetKeyDelay, -1, 110
Send {F11}
Return