Like appleman said there are different views on this. Actually i would say views as I do believe more 02 is better but with these size batches as long as you stirred really good there is sufficient 02 in the wine to give a very good fermentation. Ive been doing the lid snapped shut for many years as I have a cay that likes to either sit on or get into things so putting a towel on top or lid loose is not an option for me. I have never had a problem with this ever and all my wines ferment down fine with no stress on my yeast. If you have nothing to worry about in this area then give the wine some more 02, if you think theres a chance of a cat or even worse a kid getting into this then by all means snap it and airlock it and dont worry one bit!