Installation analysis of hdpe pipe using moses software

I am working in a project "installation analysis of long deep sea hdpe pipeline". The pipe is 3.5km long and some fraction of the pipe are wrapped with studlink chain, for towing of the pipe i am using 2 barges at each end of the pipe, now in order to keep the pipe in horizontal position i need to use some buoyancy floats for which i was using "clump" option with negative value but it is not serving the purpose.

can you please suggest any other option of adding buoyancy floats.