The 25% of the altcoins should be diversified as well, it shouldn't be just Ethereum, Ripple, or Litecoin.
The problem with having only bitcoin is that you have put all your investments in one basket. You can't count on bitcoin to always perform like it did a month ago. You're still taking risks, and you can reduce your risks of losing by hedging against bitcoin with altcoins.
But the majority of the portfolio should still be bitcoin.
having your eggs in a basket that doesn't break your eggs is better than putting a couple of them on hot air balloons that are going to burst at any moment.
you say 25% i say either don't or if you do, remember to enter only at the bottom and dump the altcoins as soon as they rise. the dumps are as real as the pumps.