How to get radius of a spline in animation nodes? Similar to Is there a way to address the shrink / fatten / radius values of individual vertices on a curve with animation nodes?

I've got one main spline that acts as a driver. This spline will have many child splines that are copies of it, but the children should be offset based on the parent's size. Higher radius -> bigger offset.

The problem is, I can't find any way to access the parent's radius at a given point. Get Spline Samples and Evaluate don't have this information.

The Spline Info node can access radii, but it returns one radius for each point in the spline, and ideally the children will have much higher resolution than their parent. Is there any way to interpolate between values like the Sound Falloff node does for spectrum data? Is my best option to make second "helper" splines to store the data?
In the new beta v2.1, which you can download from the release page, the Evaluate Spline Node returns the radii of the samples: