As the hull is difficult to close...

Just a little trick... ;)

More the hull and the line will be near better will be the result wanted... :)
That want not to say that the Hull is good but it's a solid! :)
https://moiscript.weebly.com/uploads/3/9/3/8/3938813/brede3.3dm
ps Not "Trim" but Boolean Diff of course else hull will be not closed! ;)