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"...
I believe the Classic Barnegats are a Feather Edge style sneakbox, a shear side is flat edge. Here is a link to an article that describes the styles. https://www.facebook.com/groups/OceanCountyMemories/posts/1564366930652675/