That little spring should contact the top of the plug. Mark the boot skirt position on the plug. Then Measure the depth to the spring inside the boot with a toothpick, and compare the measurement with the plug dimension above the mark you made.
Using a plug with a longer outside isolator may have overcompressed it, but probably there is nothing to worry about. The engine will function if the spring is too short, though you may generate some extra radio interference due to the spark jumping the gap inside the boot.