OK, researched some Seastar cylinder info...outcome was inconclusive...
Emailed Seastar support. They responded fairly quickly with a chart that contradicts the chart that I posted.
It shows DF200A uses HC5358-3 mounted under the tiller arm with the HO6001 tie bar. But the Single install shows a HC5345-3 mounted over the tiller arm.
I found the chart he emailed me in a newer rev of the Installation Guide (rev G). The Hydraulic Steering Selection Guide says HC5345-3 with a HO6001 tie bar.
A big wrinkle here is that I do not have a Seastar brand Tie Bar. The tech support guy noted that it wasn't an HO6001(I sent a picture)
He did say "The HC5345-3 is designed to fit on top of the tiller arm.The cylinder you require is the HC5358-3.You are also using some sort of after market tiebar and I am unsure if the HC5358-3 will work with your set up.I have attached some info for you."
So basically, I have to wing it.
An HC5358-3 is an HC5345-3 with the "pivot plate" inverted. This causes the cylinder to sit higher (thats what I want).
I have an HC5345-3..mounted under the tiller arm.
I can try moving it to the top of the tiller arm. (this may cause interference with the cable conduit).
I can try removing the pivot plate from the cylinder and inverting it and then mounting it to the bottom of the tiller arm.
If I do these things the tie bar might not mount without interference. I might need to get an HO6001 Seastar tie bar.
Here is a pic of a HC5345-3 mounted on top of the tiller arm. For clarification, the "tiller arm" is part of the motor that turns the motor. In the picture it is white and just above the second "S" in SeaStar
The "Pivot Plate" mounts to the tiller arm.
here is a HC5358-3. Notice the center bracket ("Pivot Plate") is flipped vs the HC5345-3