10% seems really high. See, if around 2 or 3% is considered usually maximum healthy premine on altcoins, why should buy-inn be any bigger?
The 10% number came from our discussions with DGEX. 10% max investment is what they used for their previous managed pre-sale and what they suggested we implement. We decided that we would take their advice and go with the recommended number they chose from experience.
DGEX did it once and it didn't explode. Also, as I assume DGEX will get compensation based on the amount of invested BTC over DGEX, there is a collision of interests.
Should compensation be based on the amount of invested BTC, the 10% is more self interest than interest in the well being of the coin.