I doubt it TBH, if you change your mind and decide to check in the bag on the day it'll cost about €9 return I think, from what I saw the last time I flew ryanair, people were checking in the bags, were issued with a bill, paid it at the ryanair reservation desk and came back to the check in desk with the receipt and got their boarding cards. They didn't seem to be queuing up again, usually their travelling companions stayed at the check in desk to hold their place in the queue but left people through who were waiting behind them for check in. I did find them quite liberal about the size of bag they allowed to check in, when I booked I paid for one bag and my other half brought a carry-on but we were flying back late at night so I decided not to bother checking in my big bag I carried it on instead. There wasn't much space in the overhead lockers due to more people bringing carry-ons we sat in the very back row (safest row on the plane I believe) but had to store the bags about 5 rows down which was a nightmare when the flight landed and there was the usual rush to get off the plane and retrieve bags