Nice Guns man.
As i said in your earlier post...thats a great light weight for a 10...a heavyish game gun nearly.Great for game & clays with sensible yet ooomphy loads.
Then you have that nice "lump"

of Bates for the still sensible heavier loads...your sorted mate..nice.
I have not yet garnered a 10 bore...but would like on of the light short chamber ones like your lovely Francotte
can't help with your qs, but wanted to say "NICE"
Couldn't you modify a mec 600?....trim a 3" shell & do the old Hartin Crimp.
Still a bit furry from last night..but others will have it in great detail I'd bet
Franc