I don't mind the occasional terminating stream -- heck, it's reasonable that not all rivers cross all mountains (see the Continental Divide in the USA), but it's more like I have yet to find a river that crosses any mountain zone in 1.7.10 when RTG plus CC/mountain chains is active.
That's actually intentional - the mountain zones break the rivers into basins so most of the time you'll get rivers flowing logically from a mountain source to some at least half-plausible destination like a swamp or lake. It also makes the brief terminations less common. That said, besides the fact that it's a good approximation for maps, it would be hard to make rivers *sometimes* cross mountains. Always is easy (even if it often would look ugly), never is easy, but sometimes is hard.
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I found the correct page by going to http://cauldron.minecraftforge.net/
then go to the Downloads page, and follow instructions there