The ball link connections at the throttle servo are a good thing. Changing to a regular clevis would not change the amount of vibration, but it would permit a loose fitting clevis pin to enlarge the hole in the servo arm, reducing throttle response and accuracy over time. Gassers have strong combustion impulses, so vibration is a given. Glow engines have more but it's on a higher frequency and therefore not as visible. Just as damaging over time though.

Wide variations in engine performance in ground versus flight locations can be attributed to many different factors. The first two that usually come up are: Is the engine warmed up prior to take off? If not, the engine will always lean out to some level after take off, causing the appearance of a change in needle settings. They didn't change, the engine simply reached it's correct running temperature. The next is: Were the needles adjusted (tuned) for the best performance with the prop and fuel mix? If not, then poor flight performance should be expected. Another is: Was the carb tuned with a warm or cold engine? If it was tuned cold then the needle settings will be wrong for a warm engine. This happens much too frequently when an anxious owner gets in a hurry to set the engine tune and starts in on it immediately after starting the engine. Let the engine warm up for a minute or two before tweaking needles.

I secure any wires or group of wires that are "flight critical", which probably means all of them. "G" forces place increased loads on anything, including wire connectors, so increased load factors occur on connector pins and wires just as they do on anything else. It's always a tragedy when a wire pulls out of a receiver or elsewhere for an "unknown" reason. Things flopping around inside a fuselage place a lot of strain on themselves so securing them so they don't fly around is a good thing. They don't have to be rigidly mounted along their entire length but a cinch here and their to limit motion is good enough.

The lower blind nuts are not needed if the hook arrangement is still used.