Having done a little bit of research online, I very quickly established that it was recommended that you put bases on man o war models, as it makes it a lot easier in game. And although there is no official rules I quickly established that using different WFB one's are about the right size. So with the size being established I'm going to use plastic card as it's a lot thinner, which I think it will look alot better in game. Plus I'm also going to magnetise them for storage as I think this will limit any damage that might happen in the future. You can easily get magnetic strips online on ebay, very cheap and personally something that I highly recommend.