Just a comment:
I am not so sure that construction of this type of structure should be undertaken in a horizontal position, first off it certainly was not done like that originally.
secondly just think of the angles and bracing that needs to be permanently placed in exactly the right position horizontally so that when upright all the 4 corners are angled correctly.
I would encircle the erection site with scaffolding, tying and staying them well, and at the very top place blocking to hoist the prepared timbers into a vertical position for fastening .
Churchtowers are a good example of preparation, hoisting into position, I expect by the use of a gin pole (at that time), and surrounded with wooden scaffolding. I am sure that they were put together piece by piece,, and then worked on their exteriors from the scaffolding.
I can remember well the hydro towers (110 ft high) being erected vertically piece by piece using a gin pole and horse power, things went along pretty smoothly, and hundreds were built this way. You would think that if horizontal construction was better they would have used that method.
It would be nice to hear other comments