Very interesting stuff. @Marc_McDonald if you’d like me to reprint that part for you I’d be happy to do that for you at no cost. I no longer have Red, though. I have dialed my extrusion steps/mm by 0.2mm compared to how it was before. I’ve also got a finer nozzle (.35mm) as opposed to the 0.5mm I had before. Maybe it will print better? I have noticed, though, with parts so big, that the differential cooling rates of the plastic REALLY do start to take effect. So just the less extrusion might not solve the problem entirely. I’ve also adjusted some other calibration values on my machine since I printed your parts. Not sure if it’s better or worse, but it’s printing. 
@Eclsnowman Thanks for the information. The panels rattle slightly 3mm used with the spacer plastic (have added a few pieces of clear plastic to reduce the rattle - work well).
I been running the the break in code for several hours over a few days and noticed improvement each time I ran it. I will continue to run it a few more hours in between my tuning sessions. Now it is down to a very small vibration on the Y axis, X axis is great (no vibration).
Nathan printed all the parts in ABS for me but seemed to have more extrusion in the bushing/bearing locations. There was far too much over extrusion in the double carriage to soften and push in the bushing so I CNC bored them out to a close fit. I have new part ready (waiting for another set of bushings to arrive) and will try the acetone soften method.
I did attempt a similar approach (flexible fibreglass rod) but removed in favour of an elastic band support while I work on improving the Y axis. I will try your mounting method next.
I am loving the feedback, keep it coming and don’t be shy. I want the criticism more than accolades. I want to make it better, stronger, faster 
@Nathan_Buxton Thanks for all the information, I see that calibration and adjustments can make a big difference in part print quality. At this time I have a replacement part already printed and will see when the new bushings show up, will try the Acetone bushing install method on it. I am printing a modified spool holder at this time and will see how it turns out.
@Eclsnowman Have you considered using bearing inner race spacers on the X, Y and Z bearing / GT2 timing pulley assemblies?
I see issues with the timing pulleys pressing up against both inner and outer bearing races and attempting to rotate the entire bearing in the bearing support. This seems to cause some of the vibrations I have reported earlier. I am currently modifying the bearing mountings (X, Y and Z) to add the space for the inner race spacers to keep the timing pulley in the same locations and out of contact with the outer bearing race.
Was there a reason the Z bearing holder base was designed with a small space between the Z rail and holder? I was planning on removing that space and enlarging the Z bottom bearing holder.
@Marc_McDonald now that you mention it… Shoot I did have to buy super slim precision shims to space the pulley out from the bearing. I got them locally and forgot to add it to the BOM.
@Marc_McDonald @Eclsnowman Those shims could quite easily be printed eh?
I spaced it to allow for adjustment. At the time my printer was less tuned (it was a corexy) so I didn’t want to get into a situation where I could get close enough and hence cause binding.
@Tim_Rastall that why your the master and I am the student. Why I never thought of that floors me.
@Eclsnowman I’ve just thad a slight head start on you. Your work is awesome and you’ve clearly got a greater aptitude for finishing stuff than I do, hence the success of the Herculien, super Kudos to you man
@Tim_Rastall yeah, but your new bot looks like a screamer. I have some catching up to do. I can see your tail lights… But just barely
For those surching for the V-slot wheels and extrusions in europe , my tip : dont go for the UK-/france based suppliers, their shipping costs are redicilous, go for http://ratrig.com/
in portugal, they produce the V-Slot Linear guide rail system themselves.