use artcraft. best chemical company !
i find 5x7 and 8x10 very easy to work with. smaller plates i find harder than the bigger ones actually. they are too small so it feels like all the pouring happens faster....ie it just takes less tiem to travel end to end on a smaller plate.
5x7 is y favorite and most used wet plate size. enjoy.
did you also get coffer's manual. an invaluable resource.