Thanks for the advice. I am indeed planning to run the 600's with 3:1 reduction.
Regarding WTC, I am building my own using the lower 2/3 of a 6" diameter acrylic tube, around 9" long. It will have an old-school flat top adhered with silicone for slice-out removal if necessary, with a lid access hatch using a 3.5" endcap. My ballast tank (pictured below) also incorportates a section of 6" tube with a curved top It is 22" long and 2.5" tall at the lid peak, keeping it's usuable volume below or at the desired surfaced waterline, and has a capacity of 3.3 litres or approx 9/10th gallon.
This is the largest object I could fit in the hull and still be able to remove it. The idea was to start big and cut down if necessary following sea trials. I would add for Jungleward and others considering that the 80 is a Monster and until you've tried to handle it or put it thru a car sunroof you might not be able to fully appreciate the significant difference between 80 and 57.
The 80, which is around 1/60 scale, does have some advantages- the Aurora FS-1 is a perfect fit in the bay, and a 17-yr-old car with Cadillac fins sticking thru the roof gets Ferrari stares!