User blog comment:B214/Question and Answers 6/@comment-29362784-20170330063410/@comment-10330822-20170413072411

You mean if he like activated DxD without using CxC and BxB? I don't think it really would do anything aside from make him weaker. By fusing all his abilities together, he makes himself even stronger than he was before. Plus, I don't know if Issei is even strong enough to use Ophis's infinity power without at least the Scale Mail on.