I agree with gordob.

1. The 0.01 BTC minimum invest is only useful to for new investors to build up trust but otherwise a ridiculously small investment, not worth it. Administration cost is higher than your profit. Your history may be sufficient to justify the higher minimum investment.

2. Perhaps investments should happen on a monthly basis. Perhaps all investments could be returned on every month's first day. And deposit would only be possible until every months's second day. Or something like this.

However you decide is best, Gladimor, I am happy you are around here offering your services!