If they are getting too tall, it sounds like they are reaching for the light - have you got them in shade? I wouldn't cut them back during the summer, as you will lose the flowers if you do that. (I'm assuming this is Sedum spectabilis).

Buy or make a simple plant support to stop them falling over when windy etc.
I made some out of bits of willow after watching mine fall all over the place after last years rain.

According to a BBC Gardening programme Sedums do respond well to a chelsea chop. It means cutting back in May to allow the plant to bush out. If light or lack of is not the problem then maybe you need to move the plant to where the height (which is in its genes ) is not such a problem.

Yes, try the chop, give it a whirl. Can't remember if it's supposed to be half or third, go for it.