70-75 degrees is a little much for many tests. I'd look at 60 or 65 degrees. Also a root gap of 3/32" and land of about the same. The higher you go, the more heat that builds in the plate since heat rises and the more likely it is you will burn holes. Start a little low and use your arc force to keep the heat in the puddle and create your key hole. But some people think that a key hole is supposed to be large and visible. It really isn't. The hole should just start to oval out when you step forward(whip). I am not sure what you are referring to about the end of the electrode being past the back of the plate vs. beginning of the land at maximum depth.