For me it would depend on what the ganache was used for. Some ganaches have a higher choc-cream ratio and are better for certain things than others. Given the quantities you suggested, I'd be tempted to quadrouple and see how you go, bearing in mind you'll probably have to double the cooking time and keep a really close eye on the first batch to see if you need more or less time. Sorry, i don't have a definitive answer, that's just what I'd do if it was me.