I did this once to keep the mainline as straight as possible. I had to go over a wet area to do it and the mainline was 25' high at the upper end. I used ratchet straps to lift it into the end tree and secured it by making a loop with the mainline wire around the tree. At first I supported the mainline with pvc pipe and eventually used tie back wires to suspend it rather than support it. I tied the pipe to the mainline wire while it was on the ground which made that part of the install a lot safer.

The ladder work was tricky because most of it was done on soft ground. What I did worked but as I learned more about installing tubing I wished that I had gone around the wet area and ran the mainline closer to the ground. I was lucky, I didn't have to lift sap to the mainline. In my situation the lateral mains ran down into it even at the high end.

My recommendation would be to go around the low area if at all possible. It will make life a lot easier when it comes to maintaining it.