You can only increase the percentage of future profits you can transfer, not existing cash reserves. To do this, go to Profit Transfer under your Corporations page. You can increase Profit transfers all the way up to 100%. Only negative effect is that the corp may lose "value" making it easier for someone else to come by and bid on it. It may also incur debt because it doesn't have the cash to weather lean times. 80% is a good starting point.