DURITZ.

A bank is a bank.And if the bank goes,then all is lost.
Unless you have a reserve bank.
At your suggestion of 22% strike rate,there is a 1% chance,(yes-A hundred to one),of there being a losing streak of 60.
That is over a run of 100,000 bets.
So if you ain't daunted by the prospect of a hundred to one chance of your bank being wiped out,then 1.5% of your bank is quite in order.
OR IS IT?

Problem arises if two long losing streaks occur close together.
Supposing we just had a run of 30 outs,which will happen.
Then a winner or two followed by a string of 30 or so losers.
I suggest that this scenario is also about a 100 to one chance.

So your answer is 1.5%,if you can handle a hundred to one chance of losing your bank before losing your life.
100,000 bets is a lot of bets!