bsprague wrote:
" tripod rated for 40 lbs and a ...gimbal head rated for 55 lbs"
The OPs camera and lens are about 4 pounds. A common rule of thumb is to look for tripods that support about double. The Manfrotto I suggested supports 8.8 pounds and the carry weight is 2.4 pounds. The carry weight of the Nest tripod and gimbal is maybe about 8 pounds.
I think the OP is trying to go lighter!
That is an old myth when load capacity was important because lightweight tripods were flimsy, in the days before carbon fiber.
This explains the relationship between stability - a feature harder to engineer in a less costly tripod than load capacity - and the size of the base plate/top leg tube diameter:
http://blog.reallyrightstuff.com/choosing-a-tripod-part-1/http://blog.reallyrightstuff.com/choosing-a-tripod-part-2/http://blog.reallyrightstuff.com/choosing-a-tripod-part-3/Load capacity is only mentioned in passing. By design, a tripod stable enough to hold a 500mm lens steady is going to have a great load capacity. But a tripod that has a great load capacity does not necessarily hold a lens stable. The key is the amount of magnification - you need more stability as you go past 1:4, all the way to 1:1 - regardless of how much the camera and lens weighs.
The Gitzo catalog has a similar design philosophy, seen in this catalog on pages 14-15. They make a direct correlation between stability and tube diameter - again, no mention at all of load capacity.
Buying a tripod using load capacity, tripod weight, material other than carbon fiber - is certain to result in an under-performing, but likely affordable. But what value is getting a cheap tripod that won't hold your camera steady when you need it to? It's money down the toilet.
Given the lens and camera stated for this use - a D750 and a 28-300mm - this lens at 300mm is fully extended, and places a pretty heavy eccentric load on the head, so care must be exercised to ensure that a ball head will have a ball large enough (more friction space) to permit the head to lock down and not have the lens pull the lens down. If you have a head that is not up to the task - and i have not seen anything other than the Sirui K40X ($160) and the Feisol CB50D ($160) that is less than $200 and can hold that combo without slipping or tightening the friction knob to a point where the knob breaks or the head locks up. There is no way that a $250 tripod with head would provide this level of performance.
On the other hand, if weight is not "that" important a consideration, there was a Benro that was on sale for around $350 (used to cost around $470) that included a decent ball head. It was a little heavier, but very well built, nice workmanship (as is the case on all Benro products), and at the $350 it was a real steal. I just looked at the pages on B and H and it is no longer listed, and i have forgotten the model number.