The tunnel to surface command was made for specific needs to check a surveyed tunnel surface vs. a tunnel template as a flat template. The check was for overcut and under cut of the tunnel surface. If you want to create a tunnel the best way ist to draw it with MSTN and then import the graphic to the template library. Here you can set up the point constraints. If you need an example drop me an email
Gunnar.Pech@Bentley.com