pblais ,if you ran all lines from boom to topping lift pulley at top of mast yes the lines would not be parrallel with mast but I have said measure for example 2 metres from top of mast down topping lift halyard
,run line from here down to boom ,under boom and back up to starting point.now that line is parrallel wth mast ok.now measure 4 metres from top off mast down topping lift halyard , from here run a second line under boom and back upto starting point.
you now have two lines with main sail trapped with in and both lines are parrallel with mast.
topping lift halyard is holding boom up ,hoist sail ,sail is now holding up boom so ease off on topping lift halyard and off course bruce jacks have also gone slack allowing sail to form correct shape.
It is the same system as a dutchman but instead of one line weaving in and out of sail this system has the lines on each side of the sail.
I have now fitted new sail cover
on boom,love it . when sailing i can now see all of sail . before trying to put reef in main was a nightmare,boom bag covered bottom off sail track ,pin to stop sail slides coming out off track and if jiffy reefing line and pulley on boom was chewing up sail or not.