I could well be wrong Thilo but don't believe B+W do a 20ft Norway,its 18ft in their catalogue,same for the Powerlite.The Experts went to 18ft and the original Walkers 17ft6 in,Cairngorm I believe also 17ft.As ever with B+W heavier end of their line ratings was/is always best,11's and 12's probably if you can find any heavy lines nowadays.The Expert in particular will probably need/want more.Older the model of rod the greater the need for 40yd DT lines.
Best of luck,Pedro.
P.s.,unless you're talking special order rods,B+W would probably make you one and may well have done in the past for some one.
Whoops!!,please accept my apologies Thilo,rather full of "Ossett Blonde" last evening,B+W indeed did do a 20ft rod in the shape of a 20ft walker.A real beast of a rod.My pal Tyke of this forum had one for a while.At least a DT 12 40yder to load it and it would take more.I believe B+W will still do them to order as would Hardy still do a 20 ft Favourite to order.Expensive tho.,and very very hard work to use.See Compy's 25 fter thread.