Tag auch,
I'd go with horisontal layers (waterline), because then you have fewer parts to glue together, and it also seems more natural to me. It should also make keeping everything symmetric easier.
The thing with the blocks depend on the type of blocks - they were probably metal, so then making them out of several layers of thin styrene seems OK, just take care to shape the block shell, or put a kind of frame around the round part, so that the blocks are slightly elongated, that should make them look better. Hope this helps, have a nice day
Pawel