Longer trains/more frequent trains needed on the Cobh line?

[comcor]

My parents took their grandaughter (my niece) to Fota for the day on Tuesday of last week. According to them, the train was full in both directions. When they got on in Fota on the way back, there were already no seats available on the journey into Cork.

Now, what was interesting about this was that the trains they used weren't at rush hour at all. They were on the 11:00 from Cork and the 15:40 from Fota (the 15:30 from Cobh).

I know from my own experience that services on the line can be busy in rush hour, but I wouldn't have thought services would be full in the daytime.

Considering these trains are operating hourly with 2-car sets, what are the possibilities for increasing frequency (presumably not good considering availability of drivers) or train length. I wouldn't have though a 4-car set would be a problem, given there are unused trains in Cork that are used to operate additional peak hour services.