Red Gum problems.
When I wrote the previous answer, my time was limited and I thought to add a little more. In America, Red Gum comes from the center of HUGE Sweet (white) Gum trees and in years long gone, the "Red Gum" was sold as "Cassiniian Walnut" - and it was just as beautiful as the real thing. There are no Red Gum trees naturally in America, tho they were imported into N CA in the late 1850's by the RR conglomerates for use as RR ties. The project failed miserably as they were not informed that Eucalyptus is not a "stable" wood until it is many, many years old and it literally "walked off the dump"! A tree less than three feet in diameter will warp and twist unbelievably! A really large one produces very stable wood and is extremely beautiful. I bought some from a place near Cajon, CA (The Parrot Ranch) several years ago and it has yielded some beautiful wood and is very stable. The owner there has a block of eucalyptus approximately ten feet long and maybe twelve feet in DIAMETER - not circumference! I was blown away. I hd no idea they grew to such dimensions.
I do know that most woods (hard) such as you have pictured require about an inch per year to completely dry. That means that if a tree is ten inches thick, it will require five years to dry - because it dries all around the tree at that rate. When I dry sich wood, I do not paint the ends, I cover them with heavy cloth or heavy paper and that will retard splitting. The same goes for small slices of cross-grain wood of any species that i'm familiar with.