MT couplers hanging up on track

You need to get both the coupler height gauge and the coupler pin height gauge. These will tell you two things: (1) the coupler height gauge will tell if the couplers are at the right height on your cars; and (2) The coupler pin height gauge will tell if the coupler pins (these are those metal curved things you spoke about) have enough clearance.

It the couplers are to low, the coupler pins will most certainly catch on your track work. So check that first. If you need to raise the coupler there are ways of doing it depending on how the coupler is attached to car or truck.

If the height is OK, then you need to bend the pin up. How much you need to bend is usually indicated by the coupler pin gauge.

Irv

My experience is that the trip pin can slide up and down in the hole in the coupler. I haven't tried bending the pin.

What is the official recommendation?

I have the first gauge linked in the post above. It works quite nicely. There is a thin (26 gauge? probably thinner) steel shim that sits across the track. If the pin just barely runs cleanly over the shim, then the pin is at the right height. The pin definitely should not be extending below the rail head.

This is what I do too.  If the pin is slid up quite a bit I will trim the part that sticks out of the top of the coupler with rail nippers,  file it smooth, and cover the shiny metal with paint or a magic marker.