Hi.
I am looking for a specific type of tripod head which should be relatively cheap to make and, IMHO, relatively cheap to buy, but I can't find one.
I saw one of these at an air show last year, so it does exist, but if it can't be bought, then it must be home made. I have a good idea of how I can make it, but if anyone knows of any on-line instructions, it would save me some time.
The advantage of this head is that it supports the weight of the lens below the level of the pivots, and if the weight is central over the horizontal bar, then it can be quickly and easily moved, so as to follow an aircraft across the sky, for example.
This is my drawing of it.

Thanks for any help.
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