Saddle height help

I decided to design and print some parts to help with bike transport. As I remove the saddles when I have to fit two bikes on the carrier on the car I was always struggling to it the saddle posts at the right height again.

One part is a ring that fits around the saddle post and is clamped with a M3 bolt and nut.

The other two parts are plugs that I place in the postholder during transport to prevent dirt entering the bike frame with the saddle removed.

The parts are designed for posts with 27.2 (plug A) or 27.3 mm diameter (plug D), letters used to identify the bike it is used for. The ring is designed for a 27.2 mm post but it will fit slightly narrower or wider posts as well.
The ring has a little cam that can be used to align the saddle. This can be cut of.