Thank you for the link! When you built your boat, did you use the R/C components from a boat that was already made or did you just buy them separately and install them?
I have seen some really cheap R/C boats around at various shops for like $30 or so (the toy ones, not the expensive hobby ones). Would those work to strip out the components and put them in?
Now I have a hot glue giun and access to sufficient workshop space, I think it would be reasonably easy to do. One would only need to drill a couple of holes in the Playmo hull, for the propeller and rudder, possibly only one if these are combined. Hot glue should provide a watertight seal once you've fed the components through.
It's not on my list of priorities to create an R/C ship, but I've got open water not too far away for trials, a creek running behind my garden (and on my property), though it needs a bit of clearing of weeds.