You can increase your BTC holdings buy converting it to LTC when the LTC/BTC ratio is low, and then flipping to back to BTC when the ratio is higher.
That is extremely risky. Litecoin is a highly volatile currency. Remember, many months ago it was trading at 0.0025 against the BTC, but then peaked at 0.05 vs BTC. That is a rise of some 20 times. But at the same time, nothing prevents it from dropping back to the 0.0025 levels. Most of the Litecoin based ventures have closed (LTC-Global, Atlantis.etc). So the currency is in a very weak footing).