5.184BTC for 8 shares - 3.992BTC for 4 S1s = 1.192BTC profit from the sale of 8 shares
1.192BTC profit from sale - 0.56BTC for 2 months of power at current BTC rate = .632BTC + 144Gh/s mining + 20% ebay sale would be your total profit
If you just mine for yourself, it would probably take you around a week to make .632BTC at 720 Gh/s. Why would you want to answer to shareholders for such a low return stretched over 2 months? Just work for yourself. Any down time is your loss. Down time with shareholders makes angry shareholders. Do you plan on having 24 hour monitoring? Are you going to reimburse for down time? What if a miner or all 4 miners break down for a total loss? How will you reimburse you shareholders because there will be no mining and no ebay sale?
You're looking at a hassle and a headache for a lot of work with little pay!
your are right nice math skill's. I will cancel this.