For the double bass I have used a number of existing models, but have always felt free to modify what I thought I needed to. I have also created some of my own models, but have largely stuck to models such as Montegana, Tarr, Maggini and Rossi.  The Montegana model has been the most prolific, but as it has served me for many years, a considerable evolution can be noted over the years. In the case of the Tarr I have not varied things much other than making an arched back instead of the flat one of the original. The Maggini remained mostly original except for string length. The Rossi was scaled down universally and later underwent a revision of the slope of the shoulders as well as details at the neck joint. I have introduced detachable necks as an option on all models, but mostly they are found on the Tarr model, the most recent to be introduced.