I've recently equipped my Robbe type VII uboat with an Accurate Armour conningtower and I just wanted to write down some advice for others that are planning this mod.
What I found out during seatrials is that the Acurate Armour tower is very heavy causing the boat to roll from side to side in an unwanted way.
The tower is made from very heavy thick walled resin and what I did to fix this was to use my Dremel and remove lots of resin from the inside of the tower. I left walls about 4 mm thick and by doing this reduced the weight of the tower with one third of the original weight.
The tower is despite this mod quite heavy, about twice as much as the original from Robbe. The boat however works properly again but if a wave hits it from the side it tends to roll over a little anyway.
/Bjorn in Sweden