Dual E120 Classic to e125 helm upgrade

[Mountain Boy at Sea]

First and foremost, thank you for the quick and comprehensive response, Chuck! This is extremely helpful for planning and selecting, especially with the links you provided. I will work with Sea Ray to get my hands of an installation interconnect diagram - was just hoping....

You were absolutely right, my product designations were inaccurate. Problem is I am living 300 miles away from boat, and the Sea Ray manual doesn't have the correct original install diagram, so I started digging through electronic files....

A1: Thank you! will post a general follow up Q on Systems Diagram thread

Q3a: Got it, but why is for Downvision the 20% deadrise not material, eg. for depth? Am I overthinking this?

Q5/7a: I have a simple legacy Airmar plastic depth/temperature transducer, no frills, which per Sea Ray manual is connected to the Cummins/Mercury SmartCraft Stbd DCM module and SC5000 System View. However, I have read-out of both temp and depth on my E120s. Does this imply that my SmartCraft is interconnected with my SeaTalk x? As recommended, will touch base with Cummins. Again, your recommended post is very helpful!

Q6a: it is indeed a SR100 - therefore compatible. Is my assumption correct that I can connect directly to one of the e125 hs network inputs, and the weather data will be available on both e125s? Or do i need to go through a switch to have the same sharing effect?

Q9a: Autopilot is a ST 8002 as you suggested, and works fine. However, I don't know what course computer is installed at this time. I know I have a Fluxgate compass. Clue from the commissioning guide: Since I always use MARPA function on radar, seem to have G-functionality, my best guess is S2G or S3G. What's the relevance with regard to the E120 to e125 conversion?

Thanks Chuck, I will keep hammering away!
Heiri