Hi Shi

Going as short as possible doesn't necessarily result in the best performance.
I see it over and over in lots of SUPsters.
There's a balance between length and performance, that is deceptive at times.
You are very tall with about the same weight as me, but stability may equalize if you are younger than my 70 years.
I do fine on my 9'2 Speeed, the float is there at 148 liters... but at you height, may be a challenge.
My 9'4 Creek is also 148 liters, but at a full 32" wide is more stable and IMO, more shortboard performance due to outline and rocker.
Both boards are very different and either will give you great performance in good or iffy waves.
I have plenty of video's on both boards at my YouTube Channel:
Well, the link didn't work... so on YouTube, search Rick Weeks "Creek" or "Speeed"
I have never surfed the Slate, so no info there, but it looks like a really nice board.