That covers what I did. Adjusting the drop targets isn't hard, but was necessary in my case. The ball was getting caught when the drops were down and would get stuck. The drops couldn't go up when the ball was trapped. It was an easy fix, just adjust the drops so they are level with the playfield.
Relocating Loki takes a bit of patience as it's a bit of a pain if I recall correctly. Basically unscrew Loki and move him forward. That will twist him sideways a bit and then you will be able to see the IM right outer loop and Shield target. Sounds easy, but I recall I had to remove a screw that was held by a nut under a plastic and I didn't want to remove everything to get at it. If I recall correctly, I used a small adjustable wrench (really small to hold the nut in place while I removed the screw.
Stern released a couple of fixes for Avengers.
1. Fix for the Loki locks. It's a small sticker that goes over the rivots by the Loki locks.
2. Black Widow ramp. A couple of plastics go under the ramp where the ball is diverted to drop to the Hulk saucer. This addressed the issue of a ball missing the saucer if the going too fast.
If your game doesn't have those installed, contact Stern and get them.
Enjoy the game. It's a much better game than it gets credit for and is a hell of a good deal right now.
Cheers,
Duane