With "Must remain" I mean here the minimum on the account under the assumption that you do not withdraw more than "Available", and that the system automatically reinvests the rest.

BTW, I've indeed forgotten a factor in the formula above - the trade size is not Must_Remain - Withdrawals, but Must_Remain - Withdrawals/sqrt(1+Profits/Capital). Sorry for that. Here's our 'officially recommended' formula for withdrawals and reinvestment:

Balance on account:  C+P-W
Available to withdraw:  C+P-W-C*f
Available to reinvest:  C*f-W/f

where C is your initial capital at the first start of the system, P the total profit so far, W the total withdrawal so far, and f the square root growth factor sqrt(1+P/C).