Burning speed issues

can anyone help with this thread?i have pioneer 112d set as slave and pioneer 107d set as master both on IDE 2 cable burning on the fly.i am using ritek g05 media burning time just under 9 minutes.the problem is when i put my liteon LH-20A1 burner as master on same IDE 2 cable it will only burn at 6x using verbatim 16x dvd-r media?its as if the liteon does not like been on same cable but all the pioneers are ok.
i have been told that the best way of using on the fly is to put 1 burner on IDE 1 HDD and 1 burner to on IDE 2.this makes sense but how come i can have a 16x burner as read and 8x burner as write and it workd fine but liteon will not?

does anyone have any idea why this might happen as i have always burnt on the fly master and slave with no problems until i put the liteon in?