Hi guys, long story short is I purchased my first boat used back in May. It has a Helix 7 DI g2 ram mounted side of console. It had ordinal B&W 4"at console, which I removed but shoot thru and power cable still there. My plan was to purchase a 7 g2n, use old DI for GPs only and down the road at some point, upgrade to a 9 or 10 and network the two. Well, considering the recent pricing with new models out, I picked up Black Friday deal of Helix 7 SI G2n with nav card for $550, and Helix 9 Mega SI are $999. So I'm looking to take the plunge and upgrade now. Question is, do you think this is a good deal for the end set up of the three units mentioned? If so, would like to get advice on the best way to arrange the three. I was thinking of moving the DI to bow, 7SI on console networked to 9 on existing ram side console. Questions are around is the the best way to utilize the three, and on instillation and set up.

1. Can both the 7SI G2n and 9 Mega SI utilize the same mega SI transom transducer? if so is it simply a splitter? or am I better off having them on two transducers?
2. Thought is to keep 9 on SI/DI & Sonar and use 7 for nav. Should I leave DI on console, and network 7 g2n at bow to share waypoints, or am I better leveraging this at console for nav and sharing waypoints with 9?
3. If I use 7 g2n on console, and can share 9 transducer, do I still utilize the old shoot thru for running speeds, or is this more trouble than it's worth, or not worth it at all?
4. The previous transom transducer was installed by professional, sits, at bottom section of transom (it's stepped down, Stratos 2010 176XT) to the right of motor, would the 9 transducer simply be placed at location?

Is there a better way to leverage this set up considering the three units? How would you maximize it? Other pitfalls or advice to watch out for?

Thanks in advance for your advice and any help is appreciated.