I have experienced the same frustration. I changed my picture to one I made that says, WIMPS FORFEIT. I don't know if it is working but I don't get as many quitter. Also, I find that most of the ones that do forfeit are higher ranking players and they wait until the last putt on the last hole to forfeit. Those are the true WIMPS.
window.post_1475039372204_9 = function(win,msg){
win.postMessage(msg,"*");
}
window.post_1475039378610_32 = function(win,msg){
win.postMessage(msg,"*");
}