Solunars by Aldebaran Sidereal Academy

When working with Transits (and solunar returns), which Radix chart should be used for reference?
Should I be using the chart in the location I was born or a transposed birth-chart to where I currently am now and from where I will be observing these transits?

The latter one intuitively seems more correct for me, but I just wanted to be sure. I assume the same rule would apply for solunar returns?

You never lose your natal chart. But (1) you acquire new angles wherever you go and (2) all new are cast for wherever they occur (and then also acquire new angles if you travel while they are active).

Thus, your natal chart (for birthplace) remains permanently active. You take transits to this chart. Also, your local angles are responsive to transits: both sets.

Solar and lunar returns are calculated for wherever you are the moment they occur. Additionally, if you travel while they are in force, you pick up second set of angles for them. For example, if you have your Lunar Return in Boston and then, a few days later, fly to New Orleans, you don't lose the impact of the chart the way it set up in Boston, but you also have to look at it for New Orleans. (Probably the New Orleans angles are more important while you are there.)