Howto convert turtle3d to path?

[karabas2011]

I try to use path_copies to place children on certain point on path of turtle3d.
but get error: is_path => false
What I do wrong?
As a workaround I use example with multmatrix (but it seems it is required more then one segment,....strange)

include <BOSL2/std.scad>
include <BOSL2/turtle3d.scad>  

$fn=20;
  wd=10.4+0.6;
  sw=5; sh=5; r1=4; r2=1; a1=acos((sw/2-r1)/(r2-r1));
			//  echo((r2*cos(a1)+r1-r1*cos(a1))*2);
			//  echo( acos((sw/2-r1)/(r2-r1)) );
		ushape1=reverse(turtle(
		  ["setdir",[0,-1],
          "ymove",sw/2,"left",
          "xmove",-sh,"setdir",[-1,0],
          "arcleft",r1,a1,
          "arcleft",r2,180-a1*2,
          "arcleft",r1,a1,
          "xmove",sh,"right",
          "ymove",sw/2]
		));  
		
		path1= turtle3d([    
	          //  ["move",6, "shrink",[1.6,1.0]],
		        ["arc",50,"down", 20, "steps", 15, "shrink",[1.1,1.0]],
				["move",4, "shrink",[1.3,1.0]],
				["move",8, "shrink",[1.0,1.0]],
                ],state=LEFT,transforms=true,full_state=true);
				
		final = turtle3d(["move", 0.1], state=path1, transforms=true);	
		
		path2= turtle3d([    
	            ["move",6, "shrink",[1.6,1.0]],
		        ["arc",5,"down", 50, "steps", 15, "grow",[1.0,1.0]],
				["move",9, "grow",[1.0,1.0]],
                ], transforms=true);
				   	  
	     difference(){
		  union(){	
		  	xrot(90)cyl(d=7,h=wd);
		    down(3)sweep(ushape1, path2);	
		    down(3)sweep(ushape1, final);
           
		   multmatrix(last(path1[0])*last(path1[1]))
               down(4)yrot(90)cylinder(d=3,h=7);
	/////////^^^^^^^^^^^^^^^^^^^	  
			  
			}
		  xrot(90)cyl(d=2.8,h=20);
		  }
//