Id say they cannot be altered, but dont lose hope. Cufflinks are not a standard item, meaning that the length between the ends can vary quite a bit. One of the great mysteries in my shirt buying life is why some french cuffs shrink while others do not. I have fought back against this problem by using the appropriate cufflinks. Therefore, on my biggest circumference cuffs, I use either silk knots or sterling knots, which cinch the cuffs close together. And with cuffs that are a bit snug, I use links that have a chain between them, which helps to provide a bit of extra space.