RE: Is this bad?
Aluminum of the same spine as your carbon arrows tend to have a larger diameter. They will not be tuned out of your bow and will not impact the same point as your carbons but no, they will not damage the bow in any way as long as they of adequate weight, over 5 grains per pound at least. Shoot away, you might not hit what your aiming at when sighted in for carbons, but you may, shoot away.