I'm a little concerned that myFXbooks is going to track equity by taking an NAV reading from OANDA verses using the following formulat

Balance + (Calculated loss or profit on open trades) = equity

The reason for this concern is that OANDA to this date does not keep a history of your NAV except on it's monthly account statements.

Therefore, if myFXbook is planning on taking the NAV on hourly intervals, that would also mean that these past NAV numbers would not show up on the graphs. Additionally if for some reason you had to reload your account on myFXbook all this data would be lost.

So, I would highly suggest that myFXbook make their solution so that it continues to use the recorded transaction that OANDA gives, and use market prices to determine profit/loss on open positions.