I have prototype Exalt tips for the NT, originally they were made without the complete face being the whole peace symbol structure. Instead, they were little fins that didn't connect in the middle. The prototype exalt tip incorporated the flow insert and the soft face as one. Unfortunately it did not work as well as we had planned. Instead I was using the tip of if with the insert part removed and it worked pretty darn well.
you can also "Shim" the insert with an oring to take up distance to prevent roll back which worked really well. I never tried the "prop rod" idea but it sounds intruiging. I had a couple other parts made up but unfortunately sold my NT before I could test them out. However, I think I will be putting them back to use very soon.