I have strong opinion that Controller MUST NOT  acceess Request.Form anyway this is interface.

I have controller with simple and testable  signature. I write controller and than view not  the contrary

public void Step2( string Name, int Age, bool skip_step )

and want be possible provide fields from html form to this controller.

in signature above int field succesfull provided to controller ( except cases when not int values entered - this interesting case too, but about it later. )
and  chackebox i think must be converted to bool (i think it very logical =))  ) 

 so i want have way for it, some kind of converters etc.

Now I have one more or less appropriate way:

use signature:
public void Step2( string Name, int Age, string skip_step )
and check that skip_step is not null
{
     if ( skip_step != null )
         // checked
     else
       // unchecked

}