1.5 ohm 6v coil eh?
i think you may have a bit much primary resistance. i'm countinh 4.2 ohms. and that will make for about 2.85 amps
and since they are a plain cermaic type. they will be like that when cold.. menaing it may start hard. using the oem ballast resistor with it's thermal properties is usually more desireable, as it is lower ressitance when cold. still. if it WAS running with that setup. no need to muck with it. front coils are all over the place these days. I have seen plenty of 6v front coils that are .8-1 ohm.
1.5ohm is almost in sidemount 6v coil territory.. :)