c90's have been been going to the elefant for years, they usually make it there and back, and if there are any problems, they are the easiest bike to fix!!
tips,
Put a gallon of fuel in the shopping basket, this will give you a good range.
Only put the lightest stuff (eg sleeping bag) in the top box.
Carry a litre of spare engine oil, you never know if a ring will go. This also works as chain lube.
Extend the leg guards, and fit hand muffs.
Fit really bright led lights on the top box, fog is a real hazard.
Use trail type tyres, work well in all conditions, and i put 46 psi (3 bar) in the rear, punctures are not good in the cold, motox tyres only work well in deep snow.
If you have the ability, modify the rear brake to cable and clutch lever operation, icy roads are easy to go downhill on then.
Remove the heat spacer from the carb inlet, helps prevent icing, also a dangly rubber flap helps keep the carb warm.
Single seat conversions are great (with a sheepskin), means you dont have to remove the luggage to fill up.
After all that, bog standard c90's are more than capable of doing the job, but i'm a pervert.
http://www.scarabis.com/Photos/AndyScand07/1240032.jpg