You can balance them like any other tire just put weights in them. The tires are not made wrong and as long as you put glue in the bead track you are fine. use a hair dryer to heat the inside foam let it expand and settle then put it on a tire balancer and weight it from their. i know you have already glued your tires but for your next set remember to cut the edge of the foam . if you look at the inside of the tire it is roundish and not square like the foam comes. that will help to balance it.
What you can do to balance them is minimal at its best, if a tire is that far off then it either needs to be trued, (which very few people have any more) I came through the era ( I still have a good tire truer thats full of dust) that truing was necessary on quite a few tires. As far as the foam is concerned I never heard of square foam. If your refering to the edge of the foam its just fine if you align it properly and nothing else needs to be said [:-]