Hallo Zentaur, zunächst mal herzlich willkommen!
I'll continue in English, though. Thanks for pointing out your difficulties in finding the support forum, I guess I'll have to improve user-friendliness (my to-do list keeps growing, lol). Anyhow, it is not necessary to register, the support fora are open to guests as well.
The "one IP address every 6 hours" rule applies to Topsites Japan, not the banner exchange. You are absolutely right. I will add that to the rules to avoid confusion.
The banner exchange: the script I am using requires pre-defined banner sizes but can handle up to three image sizes, so it's three banner exchanges in one. For the time being, I have settled for just one exchange, 468x60 being the most common banner size. In future, I may consider a button exchange (88x31) and a 120x60 (or 120x120) logo exchange.
Thanks for your confidence.