OK...kept playing with the trapdoor. I got in the replacement trapdoor and....with the 1 washer, it was hitting the wireframe above it still. You do definitely want a fixed trapdoor with the metal flap....orbit shots are smoother. Without the flap, even on a decent left orbit shot sometimes it wouldn't make it all the way up the ramp in the back (because it would hit the rough trapdoor opening and lose speed).
I went ahead and added a second washer, which...did help with the metal flap hitting, though...it still was. I don't think with enough force that it will cause long term damage but....I'm not sure. However, I was noticing it was a bit harder to get the ball in the trapdoor. Some slow shots were getting rejected. Or...sometimes getting a ball stuck ->
I went ahead and tried two things:
1. I wanted the trapdoor to stay open in a higher position. So, I took off and bent the latch just slightly which will cause the resting open position of the trapdoor to be higher. You can't go too much though or it can't catch.
It took several tries to get the right bend, but...I am happy to say that the trapdoor rests open higher and not even the slowest ball will get rejected when open.
2. Instead of trying to bend the coil bracket upward, I added washers to the bottom two bolts. #8 washers. Technically they both can't fit next to each other so one is just sandwiched in.
I believe it does reduce the travel of the coil plunger, similar to adding another washer, though maybe not quite as much. Adding 1 washer width is the maximum you can do here before the coil hits the switch above it.
Anyway....so there are only two ways I can think of to make the trapdoor function better.
1. Simply reducing the length of the metal flap. I don't see a reason why it would need to be the length it is. Even half inch less would probably reduce the possibility of hitting the wireframe above it.
2. OK, so...one of the problems is that there is simply "slop" in the trapdoor. Basically, this arm post ->
When its inside the trapdoor "door", there is space above and below it. Like...in the open position, you can move the door up still. Maybe...1/2" of vertical movement? I'm not positive that the space is necessary to have the door open and close smoothly. If its not necessary...then if like a smooth plastic sleeve were fitted over it, then you could really gain a lot more ability to adjust the door.
Basically...when the door opens, the arm moves upward till it hits the coil stop. However...the trapdoor will still move 1/2" more than that, hit the wireframe, come down and then be in the open position. In the open position, the door is now resting on top of the arm post. If the door rests too low, then slow balls can get hung up.
However, if we can remove that 1/2" of movement...then when the door opens, ...less possibility of hitting the wireframe and the exact same thing happens when in the open position....it now rests higher up so balls can more easily enter.
I was thinking of using something like duct tape to wrap around the arm post but it probably isn't smooth enough to move along inside the trapdoor.