I have an Abetta, and don't really have chair seat issues with it. I prefer my stirrups a bit on the short side too. It's just too difficult for me to go from my AP saddle with super-short stirrups.. and then try and ride in the Abetta with super-long stirrups. So I compromise.
Tell a Gelding. Ask a Stallion. Discuss it with a Mare... Pray if it's a Pony!