If you shoot a release, which I guess 99.999% of all compound shooters do these days, you can get good arrow flight and reasonable accuracy with an arrow that' s way overspined. It just won' t be as consistently accurate or forgiving as the correct spine arrow would be.

With carbon arrows, they add wraps of material to make stiffer spine arrows, so stiffer does equal heavier. With aluminums, they can vary the diameter of the shaft and the wall thickness to make a stiff arrow that' s light. But light aluminum arrows is the reason carbons have gotten their overblown reputation for durability. Those thin walled arrows dent, ding and bend way too easy for my tastes.

If you shoot fingers, having the correct spine is critical.