I don't know if anyone has been successful in RCing one of the Icons or TI Disney nautilae.
I know Bob Martin is working on a TI version, and I have an Icons/Scott Brodeen version.
I don't know how heavy the TI version is, but the Brodeen version is very heavily cast in what looks like polyurethane resin.
Obviously, they never intended it to be used as a working model, because a quick and dirty bathtub test revealed that block of foam of roughly 480ml was required to lift the thing to the correct waterline.
Hmmmmm, not a lot of freeboard on the nautilus either.
480ml equates to 480 grams of weight- over a pound for a 31" model!!!
Quite a big ballast tank, plus with that amount of top weight, I'll wager you'll need some lead in the keel to keep the thing laterally stable.
Solution? Either dremel down the original, time consuming and potentially disasterous, or remould using a lightweight epoxy glass layup.
Using the latter method it shouldn't be too difficult to reduce the top weight to 50%- a 240ml tank is a much nicer size.
The rest of the boat should prove simple, because with the cheap and readily available miniature R/C equipment, there's plenty of room inside the hull.