Hi @Anne_st
as I mentioned in my previous message, there is no "right" or "wrong" way to select the amount of regularization you want to apply. It is very subjective. The L-curve analysis is simple because you get to find the highest level of regularization that does not affect the overall fit to the data. But sometimes, if you plot your control (B or friction coefficient) you may still see that it is very irregular and you may want to apply a bit more smoothing. That's what I generally do and it looks like it is the strategy that was adopted in the paper you mention. The corner is also never very clear, so there is a lot of leeway. In most publications, people don't even do an L-curve analysis and choose parameters based on "experience". Don't overthink it really...
Mathieu