9mm linear rails vs metal V wheels (vs delrin) for custom Z-axis

I have some extra 200mm long, 9mm wide NSK rails and carriages from another postponed project. Yes, those are small and cute... I've wondered about using some of them for my z-axis. I have some 12in steel rails and steel V wheels I was planing to use, but those would add a lot of weight. I'm not sure it is necessary or ideal.

These rails are super low profile (around 10mm high), and may end up saving a lot of weight and bulk if they are able to do a decent enough job. Two of these 9mm...

9mm linear rails vs metal V wheels (vs delrin) for custom Z-axis