Looks decent to me. And the angle his ears are at is fine. When he alerts and his ears are erect (which is what they do automatically) he'll have to use his muscles more to keep them that way. But they won't tip inward, which is what you want to avoid.
I would taper the post. The further down in you can get it, the more snug it will be, and the less he will shake his head or mess with it--which means the post will stay in.
I would also slant the bottom strip of tape down a little--I start with the end of the tape on the post as low as I can get it comfortably and then slant it up to the top of his head, around and back with a slant to stick in on the post. Sorta like this:
When you stick the ear to the post, make sure the top forward edge (words are so imprecise) goes makes a straight line up the post and isn't twisted around the post.
If the post pops out of his ear, it gets wet or dirty (more than usual) or it starts to smell, you want to take the post down and evaluate. If you see any raw skin, swelling or ooziness you will need to leave them down until that goes away. And don't use alcohol to clean them if there is any sore or raw area--it'll sting like crazy and he'll hate you forever
Well, he won't like it anyway.