and I could be wrong here , but the Remington 58 was in 22" and 24" , not 18" ever .
I also don't think the extra four to six inches would make a hill of beans in weight , with a gun thats going to weight 7 or 8 pounds anyway . If you havea 14" trigger pull which I really enjoy , 22" or 24" is minimally perfect for balance anyway . Center of gravity on a gun like this is going to be the body of the gun , not the stock , not the barrel , you'd be good to go Mate .
Heck, make me one in 32 inch and you'd have a real long range revolving rifle, not no carbine . Look how long the Root is ! Theres a reason , powder burn rate of 2ff , yup .
Das Jaeger