Ah... yes, 7mm can be filled with silicone easily, but should be applied in two goes. Fill the gap first, up to the top of the tray. Keep a cup of cold water handy. Dip your finger in the water and run it along the silicone to push it in the gap and smooth it off. The water stop your finger from sticking to the sealant and dragging it along.
That's the bead that will plug the gap. Finish with a finer bead along the top of the first. That's the one that will show, and shed the water into the tray.