The HL hull is much stiffer to start with than the WSN hull ( when I cut away the battery box on the WSN it got really unstable ) , and since you are gonna do some upgrades , and the tank will get heavier the stiffening is more needed ....

The track trowing is usually ( as far as I know ) due to the idlerweel bending slightly inwars ( if its stock mounted ) when you are driving - causing the aligment to the roadweels to be messed up .... solved by stiffening chassie or/and a whole rear axel ...
never had any problems with track throwing since I got the idlerweel fixed ( and carefully aligned with the roadweels )