If you try Google, you'll find that hot air balloons rising and falling are, in fact, influenced by the Coriolis effect enough that pilots can make some use of it. I didn't know that myself until I checked.
So now you've found two more DIY ways to test for a round earth: There's the two-flight test (timing two commercial airline flights in each hemisphere as discussed previously), the Focault pendulum test, the long-range rifle shot test, and a hot air balloon ride. The last two are admittedly a little tricky as they're sensitive to conditions and special equipment, but that's still two more options for the armchair flat earther.
What I don't get is how you can look at other things like the moon, the sun, Venus, Jupiter and its moons, etc, and see that they're obviously round, and then not think that the earth is too. Why would it make sense that the earth is the only flat thing?