turnkey4099,
You must be talking about the same willows as in my area.
They seem to get to about 60-70ft tall and stop growing up and start getting fat.
My wife says I'm doing the same thing. LOL
Wet willow is like splitting a sponge but dry oh to easy.
The only elm for me that is painful is American Elm.
I split one piece until it's a string clinger, then leave it and load another to push it through.
Doing it that way it's pretty much as easy as anything else to split.
Rock elm and Red elm only rarely need that second pusher piece and for me they mainly go bang like very dry sugar maple.
Fun to launch wood into space
Siberian i have never split but i hear it's similar to american.