I would imagine that at any point in time there is a statistically safe sized bet (being a proportion of your bank) which would depend only on your strike rate and your average return which would give you a (say) 99.99% chance of never wiping out your bank. This assumes that on level stakes you can come out in front because otherwise I suggest that whatever your betting strategy the bank is going to dissappear eventually.

The answer to the second of the two questions above is simply to select suffiecient winners that you would make a profit on even stakes and the bank will eventually grow.
The answer to the first half may be able to be supplied by a statastician of the calibre of woof43. Given a 20% strike rate and a small positive POT can you tell us what proportion of our bank can be bet to give us a 99.99% chance of never wiping out?
Assuming this figure can be calculated my strategy would be to keep that same size bet during the losing streak because statistics has told us we'll bounce back and increase it in proportion to the growth of the bank as we make a profit (again because we are statistically safe). The other alternative would be to decrease the bet as we encounter a losing streak which I suppose would be safer but would cause you to take longer to bounce back.
Is there such a safe bet? or have I been talking complete bollocks?

KV