Treadmill form

So I'm finally getting back into running after a long hiatus. I'm currently using a Curve treadmill, one of the ones where you have to use your own momentum and strength to get the concave platform to move. I like it a lot better than the standard powered treadmill where you just have to keep up.

Anyway, I'm feeling good and haven't had any of the IT pain that's knocked me out for so long. But I'm having trouble keeping a rhythm while running. It feels good to let my leg swing out behind me and take my pelvis with it, while relaxing my hip flexors (ie right let swings behind and right pelvis rotates back), but that way feels like I'm rotating around like a whirling dervish. It feels more rhythmical to me to let my leg swing out but instead of my pelvis swinging behind my glutes and adductors fire and keep my pelvis more or less level with my shoulders. My knee feels fine either way, but the better rhythm doesn't feel as relaxed. I'm not sure if I'm making any sense here and I haven't really proofread so if you're confused please let me know and I'll try to explain it better.

Any ideas on form or cues I can think of? I do plan on taking it outside eventually but I started with this and I'm trying to introduce as few variables as possible as I get back into it.