Disable list "bounce" effect on Samsung Galaxy Mini
No - as you've correctly ascertained, a custom ROM is most likely your best bet. Also, the bounce effect is a Samsung "feature" - by default Android uses the glow effect to indicate the end of a list. I'm also unsure if this is a Froyo only feature, because IIRC, one of the UI updates was the glow effect, which Samsung did incorporate into their later ROM releases.