Mast step, portlights, hatches
With our 20+ year old boats, any of these structures that penetrate the cabin roof could cause a leak. (Actually, the mast step means the holes for the electrical cables, and step hold-down bolts.)Because they usually also lead to rot of the balsa in the middle of the roof "sandwich" they need to be addressed. Secondary possibilities are the hand rail screws, and any added hardware mounted on the cabin roof.It is very difficult to find the leak from the point it appears, because the liner leaves a gap between it and the roof for water to move fore and aft before flowing into the cabin. At the point you mention, any of these three could be the cause. I suppose you could track down which it is by spraying the possible sources in turn with a hose while observing the site of the leak inside.DavidLady Lillie'77 h27(Just repaired the mast step, and replaced the forward hatch)