I don't think its so much a difference between blue and orange. I have a feeling the difference in diameter is more likely an age thing. Older rope = more dirt worked it's way into the core causing expansion and more wear on the cover, therefore fluff.
I certainly know my oldest cougar is the fattest.
On a serious note, the akimbo is pretty frustrating, but kudos to Jaime, I sent him some feedback and some questions etc and he got back to me pretty quick and sent me some new parts. Ive got a new shape top cam that's not anodised and some new weaker springs for the top cam too. I put the weakest spring in and the new cam and it has certainly improved my experience on the HTP. It works like I've always wanted it to now... almost. I've not tried it on cougar since doing the mods but hopefully it improves that too. Having had a really critical look at it after changing the springs I realised that the bottom cam also plays a massive role in stopping the device self tending to it's full potential... It's kind of hard to explain but because of the profile of the bottom cam the bottom has to kind of be half engaged to self tend.. When you sit your weight into it the rope is kicked out at an angle. So the same thing is happening when its clipped into you chesty/neck tether and pulling tight against your bridge. That cam forces it's way onto the rope stopping any chance of self tending. Basically, like with everything on this strange device its another counter intuitive situation, you want a really sloppy loose neck tether/chesty. Also its worth noting that this is all probably pretty irrelevant if you've got the original spring in the top. It's not hard to take it apart though and bend the spring into a tighter V shape to weaken it. Or take it out completely. I have mine with a spring, but it may as well not be there as I bent it a bit too far. The only thing to watch out for is that with plenty of rope weight and no spring the akimbo will occasionally drop down the rope when you are not leaning back into it, it's not a big deal for me as I'm kinda used to that from worn out Unicenders and the bulldog bones. I would rather that than have no self tending.. Anyway, long story short it's getting better. Will report back when I have tried it on cougar. Also I think it's important to give Jaime your feedback to try and help improve it. I've suggested a number of things so far but it can't hurt for him to hear it from multiple sources. And regarding the rope diameter thing. There is just enough length on the bolts to take it apart and put it back together with some small washers in there to act as spacers if you so desire. I may go down that route if I still can't get it to work on cougar. Jaime has said to me that he plans to make the production version work for 11-13mm
edit: good shout on the leverage thing by the way (James I presume), the bulldog has a really controllable nature because of this.. I honestly thing Jaime could do with having a bit of a deeper look at the bulldog.