Why not keep it simple, make the body with just a hole to put a dowel through that is attached to the head. Bodies and heads stored in a bag seperately.
I know 2 people that use a battery operated mower and like the ease of use and no maintenance. I would suggest using a cordless weed wacker to knock down the heavy stuff and then mow.
Theese might work better than a plastic hull. https://www.ballisticproducts.com/MagTech-12ga-2-1_2-empty-brass-shotshells-for-reloading/productinfo/3921270/
https://www.researchgate.net/profile/Viktor-Astakhov/publication/284530412_Turning/links/5d4446494585153e5935c5aa/Turning.pdf
Printed 2011 full PDF, hope it is useful.
I have aquired a 2001 SBDB that needs a motor board Have researched the forum and found Steve Sanfords Motor Board Details https://duckboats.net/community/threads/motor-board-details.334141/ I do not see the overall length of the motorboard. I have a 15" mercury 15 hp will start with a 2"x10"...