Fellas, just saying this plant needs very enriched soil to reach its potential.
A lot of it .
If one cannot provide that ...then a T-rex is a good alternative.
I am not denying the size at all.....I know the plant is a thug.
But you have to give it what it wants.
The plant can also be grown as a cutting.... however very young leaves are used.
Once a plant starts introducing leaves in spring you can start the cutting process to create new plantlets.
For details :google/rex begonia/cuttings/happy ending
There are some related detailed videos which there are some takeaways also.