Yes you can do a cassette box with karachaganak. Are yours growing as a true bush or semi runner? I have some planted around pole bean poles and they look like they are starting to develop runners, but the plants don't look real heatlhy. They looked like this last year too. I think where I have my pole beans planted again this year it's seems they don't do well. My bush beans however did great on this soil. I think this years pole bean plot will be bush beans from now on and where the bush beans are planted is going to be pole beans every year.