Well I guess knowing a little more about your project would be helpful then. Could you describe this model a bit? In studying airfoils, there are very few instances where you don't want to be looking at the infinite span case. You generally want to be able to make measurements at a certain chord position and have them be independent of where you are in the span.
There are exceptions, but to advise you in that regard, I suppose I would need to know a little bit more about what you are attempting. What are you trying to measure exactly?
A bit more about wall liners: they are generally made of things like hard, dense foam and take the shape of the streamlines (since streamlines on a swept wing snake across the surface of the model instead of remaining in the same span position). This removes all wall effects except for those of the wall boundary layer, which is generally very thin. As a result, outside of that wall boundary layer, the flow is spanwise uniform and your measurements won't depend on where they are taken in the span. They do typically take a little CFD to design (or other documented knowledge of the streamlines) but it is generally a simple CFD case.