I certainly hadn't considered the points you raise and the safety concerns. I will continue to remove the batteries for charging and explore the sticky tape you use.
Thank you for your advice.
Steve

It is not a good idea to charge batteries in hulls where there is no chance of air circulation and condensation can occur. I have seen the after effects of an exploding battery and now always remove my batteries to a safe place to charge. The Rx will also benefit from fresh air to prevent condensation and electrolysis from the residual charges on capacitors.
I have a friend who uses a plug socket on his deck with a shorted plug sealed with heat shrink that works well at the lake but he removes the batteries to charge after sailing.
I use vehicle sign makers sticky tape (available in all colours) to seal my yachts and have no problems.
Hope you find a solution that works for you.
Dave