Hi, my experience is that assuming you wish to keep your model boat in visual sight then the aerial length is not critical.
Make sure there is some of the wire going along the length of the boat and that here is at least 6 inches of vertical aerial. I often have a fixed vertical scale aerial with a trailing wire and socket and plug the end of the aerial into it.
This means I can remove the superstructure and just unplug the aerial.
Sorry this is not a technical answer but I have a background of electronics and up to 200 or 300 feet range it is not a problem.
I have seen many model boats where the aerial has never been undone from new, they seem to work!
Let us not find extra things to worry about! We have enough on our collective plates already!