Lane,
I think you have the right idea with the cross pin stop above the front side of the trigger and below the trigger return spring. I'm thinking of making an aluminum block to fit below the trigger return spring that would be held in place by the trigger return spring, perhaps. At first I thought of just adding some tubing over the spring forward arm but an pressure or contact on that spring will eventually result in a stress concentration point and a failue of the TRS, I think.
Removing the block insert for modification is the key concept here, I think. The way you did it is excellent, and won't create any additional problem, in my opinion. Putting an insert in without pinning it can result is some serious jams if it comes loose!
Joe