Yes, lightweight sabots will work, with a hitch.
I can accurately shoot Precision QT Polymer Tips in 180 grain, but the bullet is a 40-caliber inside a 50-cal sabot. So the extra length and slender nature of the 180gr. Precision sabot bullet puts it in-flight straighter and longer, while using that slow twist. So that's how I get away with it, out to 75 yards.
So I would suggest you visit prbullet.com and look at their QT Polymer Tips in 180gr. Again, they are 40-cal bullets inside a blue or orange 50-cal sabot (50/40).
Try a couple packs. It may work for you-too. My 1:66 is a longrifle Traditions Shenandoah BTW.