I use an MP10 on different settings throughout the day, think that may contribute to my GBTA not liking its environment since the flow is always changing?
I don't think so. I have two Vortechs, usually keep one on reefcrest mode, the other on lagoon, and my RBTA is apparantly content. That being said, it is in an area of the tank where it is not getting blasted by the current.
With regard to the above posts, I agree that keeping a nem in a tank with corals is not without risks, but personally, I think it is worth it. I have been lucky with my BTA in that it really hasn't ever moved much, and when it did it was slow (several inches over the course of a few days). Before my upgrade, it was in a 55 gallon tank that got VERY crowded with SPS and the BTA did, in fact, come in contact with several SPS's. After a few days of contact I would notice the SPS turning white in the area the nem was touching, but when I moved the SPS they always recovered. I do keep a fairly large 'safety zone' of no corals close to the BTA, but if it does start to roam I can always move the SPS or remove the BTA.
Here are a few shots of my BTA and surrounding SPS. This first one is a right-end view and from this angle it looks like there are SPS's right next to it, but the ones that look close are actually quite a bit to the left or right of the BTA (from a front of tank perspective).
Here is a front of tank shot. I can't get accurate color representation of the corals from this angle, but at least you can see how the BTA is located between the back wall and a ridge of rockwork that is barren of any coral. I do have corals in front of BTA, but there are at least 5 inches of no-man's land between the BTA at its maximum expansion and any of the corals. You can kind of see where the maximum extension range of the BTA is on the rock work (it is paler and barren of the clove polyps that cover most of the other rock in my tank).
I'd estimate my BTA is about 10-12 inches when fully expanded. It adds a lot of color to the tank, and it also adds 'movement' which would otherwise be lacking in my SPS dominant tank. I also really enjoy the clownfish/anemonie interaction. I think the BTA is actually the 'show piece' of my tank.
Good luck.