To tell you the truth being overspinned will effect arrow flight as much as being underspinned. The only difference between the two is that being overspinned will not be dangerous to shoot as compared to being underspinned. Being spinned correctly is always your best bet.
I don’t see how a over spined arrow will hurt except the added weight will slow it down. But what about arrow flight?
this is not always the case, take a look at a 2219 aluminum as compared to a 2613. The 2219 will be a lot heavier then the 2613. But the deflection at 28" on the 2613 is .265 and .335 on the 2219.