Most of the bricks are backside down so you can't actually see the backs of them. However, there are some that go along the top of the fenders where the backs are visible. Should the backs be filled in so that the bricks appear solid or should they be left as molded-hollow with no backs? Thanks

Here is a sight that has some excellent drawings and pictures of what the ERA bricks actually look like: It is all in Russian though.

Essentially it is a hollow casing with explosive inserts.

Thanks. It confirmed that there is a back plate so I need to close off the bricks that have the back exposed.