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Also, reliability is a major concern. It could be a long time (or never) before I have access to the lift again, so I also want a pre-amp with low odds of failure
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Mount the preamp down closer to the base of the tree so you can reach it if needed. The small sacrifice of noise figure is worth it. Same goes for tall towers. That was a lesson learned the hard way.
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My TV fool report indicates about a 2.5 dB improvement in WFFF at 75 feet in the pine tree, vs. 30 feet AGL on my roof.
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Micromanaging the elevation in the TVFool simulator, especially with 2-edge signals, is usually not a productive use of time. It's my hands-on observation that 2-edge signals, when actually measured, can differ from the calculated signal power by as much as 20 dB. The closer one the receiving antenna is located is to the last diffraction zone in the signal path, the wider the variance can be.
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Also a vertical stack makes the vertical aiming very critical, as it makes a very narrow beam width in the vertical direction.
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A vertical stack would be expected to cut the vertical beamwidth approximately in half, frequency dependent. Since a typical 4 or 8-bay antenna would be expected to have a vertical - 3dB BW in the 30-40° range, the vertical stack of two of them can be assumed to be in the 15-20°. Theoretically, that means there won't be a great deal of reception difference if the incoming signal path is within 7.5-10° of horizontal (assuming the mount is truly vertical). YMMV or, better yet, YAMWV (Your Actual Mileage Will vary).
If using a tree mount, stripping as many branches as you can will reduce sway in the wind (which you don't want). Try to balance the health of the tree, unless you want to sacrifice it to be a pole, with the need to reduce that swaying behavior.