From what I understand, you need the modified converter... not the standard. Then you have to remove some plastic from the tabs.
From the Tacticool22 site:
This converter requires permanant modification of your upper. The bottom hand guard alignment tab needs to be removed and the top hand guard alignment tab needs to be almost completely removed.
The back of the free float hand guard or delta ring barrel nut will almost touch the bottom portion and be .1 or 2.5mm away from the top part.
The gap doesn't bother me. I didn't mess with the tabs but did use the modified adapter. My gap seems smaller than yours.
Evolution Handguard on my SBR 15-22