Well, based on that Patrick it is not 1000 g/l of solution, it is 1000 g / liter of water which will be more than 1 liter and close to 2 Kg in weight. As you say a 50% wt/vol solution. Be careful, this will become very very hot during mixing and may boil over.
Also, I believe I said "50% by weight" , which is exactly true. 50% of the weight of that solution would be K2SO3.2H2O. It would take some calculation to find what fraction of the weight of the solution is K2SO3.