BV first off bad habit to bead check,poor advice by gunshop guy...second if your seeing two barrels your eyes are focused on the bead then when you look down range it takes a few seconds for your eyes to re-focus on the target,but agreed your a big boy,taking a new gun off the rack and expect to have the perfect fit ain't happening, same goes for the average size guy,same shotgun 5'4 he'll have issues as well on fit.,Long arms will require about an inch or more added to your franchi stock butt plate,my benelli and beretta both have 14.5" length of pull(LOP) which is okay for average sized guyz you most likely need to add another 1" + otherwise your nose will touch the rec'ver you big galoot.
if you really like your new shotgun I suggest having it fitted rather than adding shim's and hope for the best,a good gunsmith that is a shooter is a great asset if you have one in your area,call your local gun range,they most often will recommend a good smith that shoot's registerd target's you can contact for gun fit,lot's of gunsmith's around the country,finding one that shoots is where you want to go for fit,not sure where you are located but one damn good smith here in spicer minnesota is Pat Laib,he's a specialist,also builds custom rifles...
Pat usually hits all the big trap shoots around the country,not only to shoot but sets up shop for shooter's having gun issue's,not sure if north dakota has any current shoots coming up this late in the season but look Pat up,try to connect with him before he heads to AZ for the winter (he shoots all winter down there)
Another specialty gunsmith that travels and shoots is Tom Larkin owner of the
"stock shop" one on the best gunfit specialist in the country,also an avid waterfowl hunter,field gun he shoots is benelli so he'll be in the know on your franchi, last time I chatted with him,he's located in kenyon minn but travels all over for big shoots but heads to AZ after duck season,just a few thoughts.
goodluck BV...
PS regarding shooting sports we all get in slumps,most often the remedy is a new shotgun,then we customize our new toy,shoot the hell out of it and yatzee no more slump,problem solved after spending $1000's scores often rise(because we are shooting more,it's not the shotgun,rather the indian shooting...so consider a pro for gunfit iffin your a serious shooter then hit the range for a few 100 rds to bond with your new toy.
Try this excersise mounting your shotgun at home,if you have a large mirror in one of your rooms,face the mirror with shotgun in hand,close your eyes and mount your shotgun as if your going to shoot,once gun is mounted open your eyes to view how your line of sight looks,make minor adjustments as needed,cast,cant etc,maybe a drop in your case,but a good smith will help ya out.