Looking at a 2018 yesterday, my XXL Shoei Neotec fit.
Standing up as normal (top up), it fit in the center, and it fit with the face shield pushed into the top right corner.
The 2018 trunks are hard to close when brand new. I closed the lid, then put the heel of my hand on the "HONDA" logo, finger under the lip, and squeezed the trunk closed.
Last edited by PilotAlan; 06-17-2018 at 12:07 AM.