Software visualization tools face many challenges in terms of their implementation, including scalability, usability, adaptability, and durability. Such tools, like many other research tools, tend to have a short life cycle and are vulnerble to software evolution processes because of the complex problem domain and the constantly changing requirements which are dictated by research goals. In this paper we discuss the implementation of the software visualization tool CodeCrawler according to five criteria, namely the overall architecture, the internal architecture, the visualization engine, the metamodel and the interactive facilities. This discussion generates implementation recommendations and design guidelines that hold for our tool and the class of tools its stands for. We then also extract common design guidelines and recommendations that apply for other software visualization and general reverse engineering tools as well, and hope that these insights can be used fruitfully by other researchers in this field.