Designing the collar for a RIB...? in DELFTship

[Boatbuilder NL]

I am trying to create the collar for a RIB design - in DELFTship - but I just can't get it right. Anyone in this forum who has experience with DELFTship, or anyone able to tell me what free or low cost program I can use for the design phase of a collar / ponton?

Thanks!