Hello Duncan, l haven’t built this model but have built some Billing Boat kits such as the Boulogne Etaples fishing boat and the St Canute tug, both plank on frame construction. I am by no means a professional builder and have used the vast knowledge of many of the builders on this web page to help me out and they are a very helpful. But just for my six penny worth of knowledge l have carried out a dummy build of the motor, battery and Electronic speed controller, then remove to start planking. When all planking is complete l use two part resin glue to seal the inside planking (2 coats) then pour some resin in the bottom to seal the keel, bow and stern areas, l have been pretty liberal with the amounts. My first R/C model was the fishing boat which had lots of room. However my tug was a serious challenge as space was very limited, so a lot of work and head holding during that period, but a few weeks ago l did achieve a dry run test of the electrics which was successful all l need now is for my council to repair the leak in my local boating pond!
Good luck hopefully the professional guys will jump in soon, nice bunch of guys!