[ItMeansPure]

If you feel you"ll need a small get small... You may be able to massage and get enough suction in M domes but it may require overpumping to get them to stay on... Starting off on a bad foot is not good but I think if you have decent chest measurement 28 you may be able to get the M system just using one at a time not overpumping, massaging before and after and using plenty of oil...

Im not sure about your finances but maybe buy the M system and if it gets frustrating for you order one small cup to get you started...

Hope this helps in any way... Breast of luck to you!!!