@TomGracey I'm willing to share as much as you'd like to know. I set out on the project to see how inexpensively a P LTD Tunnel could be built using a Lynx hull because some of us have a few of them around. In this case I used a new hull since my others are (for now) in use. Darin Jordan was a huge help in the approach and Carl and I worked together on the electronics box. He has that kit if you're interested. My cheap approach used a Dyamite A3650-2000Kv motor attached to an OS lower, Seaking 120A Pro ESC (the flat one), and ArrowRC 5200MaH 50C battery.
The sump area of the Lynx is narrow as all Lynx owners know not knowing where everything would need to be in order to get the CG in the range I need I went with what would fit for sure and, with the ESC, what I could stack on the battery if I needed to move weight back. I now have the ESC up in the nose which opens some options for sure. I use a pull-pull which puts the cable outside the electronics box which makes getting the battery in and out much easier. The wheel is available at GrandRC.com and the Du-Bro 4-40 hardware kit. Water bulkhead fittings I got from ZippKits. Mark Sholund did a few ABC 42.55 props.
Here are some photos and you can DM me as much as you like. Next step, taking this budget build and stepping up the output a bit.
Chris