Excessive amounts of stake might be great for the short term price but not so much for the long term price.
Let's try to keep it reasonable.
It needs to be higher than HBN and lower than TEK. I don't know what people have against high stake rates. People unfamiliar with some of the high rate coins assume that there will be massive inflation, but the fact is there hasn't been - there has been price deflation that exceeds most other coins available today - and not just bubble. Look at HBN - steady rise in price and a steady rise in market cap.
Also another point is that lets say the supply and demand for CAP doesn't change, so as the money supply expands the btc/cap price might decrease. But if you are staking your coins the value of your coin holdings will increase faster than the decrease in price minus the PoW blocks that come out. So if you are staking, you really aren't losing any value in a high rate PoS coin.
Also there is a hardcoded in reduction of stake rate every 64x increase in PoS difficulty. If the upperbound is 200% and the lower bound is 1%, then at 64x the stake rate would change to 100%. There is always room to make the PoS rate change more aggressive, such as every 32x instead of 64. Then it will be much more of a market rate.
200% sounds perfectly reasonable to me, but then again I am involved with a few PoS coins and I am comfortable with the economics.
Flound what are you comfortable with?
But we also want people to mine the coin and a constant downward slope in price means it will be less and less profitable to mine as time goes on.
As long as the money supply increases at the same rate as the economy for the coin, there won't be inflation. If there's no economy, all people will do with their coins is hold them or trade for BTC.
If this was a pure PoS coin it would be different, if we're going to do this kind of staking we should probably discuss ending the PoW phase or at least phasing it out more quickly.
What I'm concerned with is ensuring the long term stability of the coin -- there's going to be a lot of pressure from speculators to do things that will pump the short term value (as you can see, that's already begun).
In order to generate interest in the coin we could also consider doing a limited time daily PoS phase like YellowCoin did. They gave 10% stake per day for 7 days I believe. This rewards the longer term holders of the coin while also generating new interest.