Fanta Challenge - 4 Robots

 I want to program the Fanta Challenge, but I want to use 4 robots instead of three.

The way I set up the sistem is this:

1. Create robtarget Start_Pos for ROB_1
2. Define movable workobject attached to ROB_1
3. Create robtargets for path of ROB_3 (using the ROB_1 attached workobject)
4. Define movable workobject attached to ROB_3
5. Create robtargets for path of ROB_4 (using the ROB_3 attached workobject)
6. Repeat process for ROB_2 (using an attached workobject for ROB_4)
7. Have each robot follow the same exact path but referencing the its predecessor workobject.

The thing is that I want the robtargets for the paths for ROB_3/ROB_4/ROB_2 to be generated only using the Start_Pos for ROB_1 (so I can reuse the code).
I managed to get all the robtargets defining the paths for each robot using a structure of multi dimensional arrays.

The problem is that it seams "It is not allowed to have chain coordinated frames. Arrange mechanical units so all mechanical units follow one unit".  ANY WAY AROUND THIS??

Defining a movable workobject for ROB_1/ROB_3/ROB_4 and then running the same path in the new workobject seems the simplest way to me.

Is there a way to work around this? Any ideas how to achieve the whole coordinated system using only 1 Start_Pos (for 1 robot) robtarget? I want the whole system to be parametric so I can only change the Start_Pos robtarget and all robots would adapt.

Thanks much,