RE: Cox Hyper Viper
I think I read that the problem is caused by assembly glue blocking the line, but that may be wrong.
Some good planes for your Norvel might be some of the Dick Sarpolus sheet wing profiles that were originally powered by TeeDee .049's. Flying Models has an online list, I think.
Another possibility would be any of the Golden State 1/2A planes with built-up wing and profile fuselage.
Also, the Brodak 1/2A Flite Streak would be good. I think most of the other Brodak 1/2A's are for Bee type engines.
I build about 1/2 kits and 1/2 from plans.
George