I have two of these in my front yard, an Ogon in back as well as a 3 meterish rooted cutting of the big tree on the right.
My old Arbor Day tree on the right seems to want to grow a bit shorter and thicker than the one on the left which was planted a good decade or more later. The newer one is probably growing faster. Does anyone remember a bit of talk a few years back about there being 3 sub types of Metasequoia? My google and duck duck go skills fail me.
I've decided to go the how many mowers tall is it method. Of course I have failed to measure my mower's height. The smaller one on the left is actually just a little closer than the mower so it's height needs rounded down from 9 1/2 mowers to 9.