I don't own a Winchester with a crossbolt safety. I have replaced the safety on one of my Marlin 336 rifles, with Clyde Ludwigs safety plug. It takes the place of the safety, and looks like a screw head.
Now, the question is "Is it safe". The answer to that question is YES, as long as I'm the one in possession of the rifle. Primarily because I have never trusted a mechanical safety. If I ever sell the rifle, I will certainly reinstall the factory safety.