In high school I built 2/3 of one of the Wilhelmshaven aircraft carriers. I used only the formers in thickness they came printed on. The ship was very sturdy, had a working elevator - and was over a meter long. I'm doing the Lutjens now - it's about 2' long - and same thing, just the stock former thickness and it's sturdy enough. I couldn't stand on it or anything - but it'll easily hold up my glue bottles and probably more weight.
I'm also building this ship from only diagrams (not sure what German instructions exist, but no English ones). It's not too difficult, although there are some things I have to study a bit and have had to guess how one or 2 things should go - but none of it is going to affect the overall appearance of the model.