Thanks to tom10 for causing me to check out the nut position on all of my rough stacks.
If you use a rough stack and decide to try the mega XL dual coils, use just a little bit of caution. If the switch nut is turned so that a flat side is facing the 510 connector, it will go on there. If a corner of the nut is facing the 510 connector, it won't. So, either check the nut before trying to spin on a mega-XL, or spin on slowly and see if it hits the nut.
It might be best to use a shorty extension and not mess around with the switch nut at all.
If you use a rough stack and decide to try the mega XL dual coils, use just a little bit of caution. If the switch nut is turned so that a flat side is facing the 510 connector, it will go on there. If a corner of the nut is facing the 510 connector, it won't. So, either check the nut before trying to spin on a mega-XL, or spin on slowly and see if it hits the nut.
It might be best to use a shorty extension and not mess around with the switch nut at all.