Thanks Mike.
You are probably right about the lateral position. At 15" it might be in line with the half-strake. But I'll check it out.
Good to know you think the distance from transom to lower unit is ok. That was/is my biggest initial concern.
I could try a temporary clamp mount, but two issues:
1) if this is definitely pushing it for the transom mount anyway, I do not want to assemble the transom mount and lose the ability to exchange with Humminbird for the through-hull.
2) a temporary mounting board is going to push the location aft by the thickness of the board. But I could do this with 1/2" ply (or maybe even 1/4"). If I'm already tight fore and aft, that 1/2" might make a difference.
Alternatively, I'm helping a colleague test his 798ci SI this weekend. We're doing a custom sidemount on a pole. I could pull his ducer off the sidemount and try that one on a temporary board. It's the smaller XNT-9-SI-180-T ducer, but might be a reasonable proxy.
The baitwell pump hasn't been used in years. Replaced with different method. So not a consideration from electrical or turbulence perspective. Good reminder to take it off though. Mostly just for spatial reference.
Thanks again.