User blog comment:B214/Volume 23 discussion blog/@comment-26285797-20170329201510/@comment-29963364-20170329202510

After the Issei vs Dulio match, Issei did tell Ravel that he "figured something out" during the match.

He did a "partial activation" of his DxD G mode.

First, he turned his right hand into that of the DxD G (you see it in the illustration of Issei vs Dulio).

Second, he turned his Scale Mail wings into those of the DxD G wings (so he had four wings).

This way, he was able to increase his abilities to the level of DxD G without using up his stamina, or going into a coma. So Issei just needs to learn how to "switch-out" parts of his CCP armor for his DxD G armor in rapid succession.