There is a glue that Graupner have long recommended for building their "plastic" hulled kits
It is called Stabilit Express. It is a two part product, a powder and a resin which are mixed in proportion.While it is quite expensive, it sticks virtually anything to ABS or similar "slippy" plastic hull materials. I have used it on two such kits with great sucess. It is super for any areas where any stress occurs. Slightly roughing the plastic before application makes it an even better joint