I have a Sidekick I use on one tripod and a full size gimbal on another 'pod.
If you have a heavy duty ballhead with an Arca Swiss compatible QR platform, I recommend the Wimberley Sidekick. It simply slips into the ballhead that's been tilted fully off to one side. I've used one for over ten years and it works well. It would be plenty strong enough for that Tamron lens (I've used it with up to Canon 300/2.8 IS and 500/4 IS lenses).
The beauty of the Sidekick is that the ballhead remains on your tripod and you can quickly and easily convert it back for normal usage. It just takes a few seconds to remove the Sidekick and reposition the ballhead. This is an advantage over a full size gimbal that completely replaces the ballhead, sort of making a tripod "dedicated to big lens use only" (unless you take tools into the field to swap out the tripod heads).
Another, unadvertised benefit of the Sidekick is that it mounts to the lens from the side... i.e. you rotate the lens' tripod ring foot off to the LH side to use the Sidekick. I discovered this also makes the Sidekick neatly usable to set up any camera fitted with a shorter lens and an Arca Swiss release plate in vertical/portrait orientation, so it isn't necessary to fit a bulky, expensive L-bracket on the camera for this purpose.
Full size gimbal mounts designed for use with the heaviest lenses position the mounting platform below the lens, sort of cradling it. This is good with the biggest and heaviest lenses, but it doesn't allow you to mount the camera in portrait orientation, as described above.
However, some full size gimbal mounts, including the one I use, can be pretty easily modified to mount to one side or the other and might serve in the same way. The platform that sits under the lens is vertically adjustable. It also can be completely removed, and the lens can be mounted from the side instead, same as with the Sidekick. I just wouldn't do this with the biggest and heaviest lenses.
Whatever you do, some other things you might consider...
Hopefully you already have a pretty sturdy tripod (and, if you choose the Sidekick, a sturdy ballhead).
You'll need a somewhat longer than usual Arca Swiss plate on the foot of the lens. This is so that you can slide the lens & camera forward and backward a bit to set up a good balance on the gimbal. Some gimbal mounts come with a lens mounting place, but most don't.
Be sure whatever plate you get has anti-rotation features. This can simply be a couple nubs on the plate that prevent it from twisting, or it might be double mounting screws, or a pin that fits into a socket on the lens foot (which you might have to drill), or similar. There's a lot of torque on a heavy lens and camera rig, so be sure there's something preventing that lens plate from twisting.
You also might want to consider a leveling platform on your tripod, under the head. When using a gimbal it's often important to have the head near perfectly level, for the panning motion. Without a leveling platform, this involves a lot of fiddling around with the length of the legs to get it leveled. Then, if you move the tripod at all, that setup is lost and needs to be redone. More fiddling! Depending upon what tripod you have, there are various types of leveling platforms. Some replace any center column on the tripod completely (Gitzo). Others can be used in conjunction with a center column (Manfrotto). The leveling platform will add more than a pound of weight to the tripod, but I feel it's well worth it for the time saved setting up quickly and easily.
That NEST NT-530H looked interesting! I have three carbon fiber tripods and several carbon fiber bicycles, so I really appreciate the benefits CF offers: lighter weight, strength, fine vibration dampening. However, I just looked up the NEST gimbal head online and see that it weighs 1336 grams. My $100 Chinese-made gimbal mount (that looks exactly the same, except it's metal... it's identical to the Opteka and Beike, too, for that matter), weighs 1180 grams with a camo cover added to it!
So, as is all too common with some unusually low priced "carbon fiber" parts for bicycles, I'm suspecting "fake".... I'd be surprised if NEST weren't simply a standard metal head clad with a layer or two of carbon fiber to give it the high tech "look", while keeping costs low. I can't confirm this one way or the other online... but if it were truly mostly made of carbon fiber, it should weigh considerably less, not more than a comparable all-metal head. Tech info on the NEST from their Chinese wholesale distributor:
http://nest.en.alibaba.com/product/544140170-213784987/NEST_NT_530H_gimbal_head_tilt_head_bird_watching_head_with_Quick_Release_Plate_and_Carry_Bag.htmlNo, you don't need anything heavier duty than the Opteka... it's rated to 30+ lbs! The Tamron 150-600mm weighs about 4 lbs and most cameras, even with a battery grip, are less than 3 lbs. That's a 4X to 5X safety ratio! (My 500/4L IS and one of my cameras weigh nearly twice as much, and I trust them to either the Sidekick or the Chinese-made full size gimbal).
The Sidekick doesn't have a listed weight rating... But any ballhead used with it needs to be pretty heavy duty. Both the ballheads I use my Sidekick with are rated to 50 lbs (Kirk BH-1 and a Smith-Victor B8). The tripod you use also needs to be fairly sturdy, mine are rated to 25+ lbs (two Gitzo 1325 and one 1348).