In both these games , the mistakes hippo players did lead to an early defeat.
Let's see which these mistakes were:
1)Early attacking in the centre
That cancels the meaning of hippo but if you want to attack the centre , be sure that there are no wekanesses that your opponent can attack.Either f4 or c4 leave e3 or d3 weak.Be sure that you can defend them.
2)Do not castle too early.
Wait to see where your opponent will castle and castle on the same side.Usually the hippoer doesn't have many problems with his king uncastled(see games Petrosian Spassky)
3)Don't allow your opponent to open rook files.
If Black plays a5 against your hippo ,then a3 must be an almsot automatic reaction so that you can answer a4 with b4 keeping the rook file closed.The same must happen if Black attempts h5-h4.H3 will allow you to keep the rook file closed with g4.
And if you are Black then you must play ...a6 as response to a4 and ...h6 against h4.
4)Don't allow your opponent to exchange bishops unless you have a good reason.
King's bishop is the one that must be protected as k-side weakens a lot without that bishop.
Queen's bishop might not be so important if the queen can take it's place on b7.In any case examine carefully the position that occurs.