When I use a SOP Import node to bring a Guide Groom into Solaris, all the curves end up linear despite the fact that they were curved in SOPs. I'm able to get them back to being curved in Solaris by using an Edit Properties node and setting type to cubic and basis to bspline, but then the guides look like they're floating off of the scalp.
I've attached screenshots to show what I mean. 1 is the linear curves, 1 is the cubic curves, and 1 shows the edited properties.
How can I change this so the guides display across the whole curve for each curve?

you can try setting the wrap property to pinned.

For BSpline and Catmull Rom curves, this wrapping option tells the renderer to add “phantom points” to the curve which cause the visual representation of the curve to start exactly at the first vertex position, and end at the last vertex position. The renderer is expected to compute these phantom point positions automatically.

Thanks for your reply frost. I tried adding the wrap property and setting it to pinned, but the hair still looks the same in the viewport.
However, in Karma it works.

I expect the curves are also just polygons in SOPs (rather than being e.g NURBS curves)
However, the groom objects have "Display as Subdivision Curves" enabled to render them smoothly in the SOP viewport and in Mantra. You can get a similar effect by turning on the "treat as subdivision" option on SOP Import

Thank you cwhite, that's a great solution!