What would you guys feel is the correct (best or proper) barrel contour for a 450 NE double rifle. would an F44 be close?

No; you will end up with a hog; .725 muzzle; ; no ready made barrel is the right contour; you will have to do it yourself. I have done this analysis before and built them. F44 would certainly be a good place to start; I have used them for 45-70s DRs. Best to copy an existing DR; two designs; like the krieghoff that has a very small breech and heavy barrels, or the English type with fat breeches and thin muzzles. That places the weight between the hands and most people like that. What are you starting with?

dpcd, thanks for your inputs. do you know where to find the British contour?, as no one near me has one to get the measurements. I certainly like the idea of balance in the hand a lot and believe the weight I am searching for is 9 to 10.5 lbs

I did find these from Ellis Brown
Rigby .450 Barrel Tapers
(5 different barrels)

Breech;___3” from Breech;___6” from Breech;____Muzzle;____Length
1.029;____________0.89;__________0.787;_____0.638;_____26.0”
1.029;___________0.906;___________0.83;_____0.638;_____26.0”
1.045;___________0.913;__________0.876;_____0.638;_____26.0”
1.063;___________0.942;__________0.878;_____0.638;_____26.0”
1.038;___________0.918;__________0.824;_____0.618;_____26.0”

Ellis450 "

Those look good; I can measure a Searcy for you if you want. It has a big breech and thin muzzles. I think you will want more than 9 pounds for a 450 unless you like recoil.

9 pounds would likely be the lowest I would consider, but I do practice with a full 10 bore often, and yes I would be interest in butches measurements. Doe he follow closely the British form?

Yes. he does.

Great will be interested in his measurements