Small arms fire absolutely can hit a hovering F35 at 2500. Lots of shooters regularly practice 3000' shots with smaller caliber rounds like .308. Their targets are much smaller than an F35. Completely reasonable. Not necessarily easy at all but totally within the realm of very possible that someone with hobby experience in firearms could hit something as large as a hovering f35 at 2500 feet.

What is your point about collateral damage? A hit is a hit. A .50 bullet hitting an aircraft can absolutely still have enough kinetic force to cause some serious damage to an aircraft. Aircraft are not tanks, this is not an A-10. They are susceptible to damage from small arms fire. They are a multi role jet including close air support but are not built like an A-10 and might be susceptible to small arms especially something as large as .50 cal. If you're referring to the pings, watch some videos with cameras around targets getting hit like car frames or washing machines. Hits are like pings. An airfarme is very rigid design with a connected structure. Although im sure the cockpit is loud, you likely have a known "normal" noise signature and when something smacks the frame of your aircraft at 2500 feet per second at 650grains your going to hear that ping resonate through the frame. Ping is probably exactly how it would be described. At 2500 feet, .50 velocity should still be around 1500fps (based on some quick research). If you mean it should results in parts flying off, well that completely depends on what gets hit, I'm sure there are spots that will just cause fly through impacts. The post says alerts starting showing up. If your expectation is hollywood fireball and flames, it's not always like that.