I do not recommend using a 2" stud for 1 3/16" post.
Here is why:
I was an aircraft inspector. We have specifications that must be followed. If you like to fly you will appreciate the attention to detail and building the plane to blueprint. Some specs allow you to work with tolerances. Some specs are hard callouts that allow no deviation.
One of those specs is that any screw or bolt had to have a minimum of two threads showing beyond the nut. Since we are talking pinball and not aircraft you can make your own leeways.
This would not be allowed on an airplane because the 2 thread minimum has not been met. But it is good enough to a pinball machine.
This is a #6 screw that I cut to size. Its has a full 2" of threads. The piece of wood is cut to 1/2" thick, the same thickness as the new CPR Catacomb play field I bought.
By installing this 2" screw from the bottom, I have enough threads left over to lock down a nut and also place a nylon cap on.
In this pic the nylon cap is removed and the cap portion of a 2" post stud is matched for comparison. You can see the difference in the thread lengths. The extra threads on the post stud are going to cause you problems.
Use a 2" stud and you are left with this. How many threads did you manage to get screwed down into the T-nut? Guess. Just guess. Can you figure it out?
Lets say you are going to look at a pin to buy and as you look it over you see an empty hole in the T-nut. Hold this thought.
The rest of the story:
This small gap between the nut on the stud and the red post is how much thread you are going to have when you tighten the stud down.
You only have about two threads locking the post to the play field. You can do what you want. It is your pin. If you think two threads are enough, go for it.
I am going to build my play fields up using a 2" Phillips head screw and the T-nut. This is the way Dothedoo suggested and it looks good to me.
About holding that thought from above. Let's say you went to look at a pin to buy that someone has built from the ground up. What are you going to think if you lift the play field and see a load of empty T-nut holes. Are you going trust that builder's construction methods?