Here is the info from the current manuals.
As mentioned pmag and lightspeed recommend very different processes. The adapters aren’t the same. If you look at them side by side, you can see the pmag has a brighter brass look compared to the lightspeed. Lightspeed adapters take 35-45 ft-lbs of torque. Pmag recommends combining adapter and plug and only using 18 ft-lbs. You can break a pmag adapter at 18 ft-lbs by not installing it with a spark plug inserted.
LIGHTSPEED CURRENT MANUAL ENTRY
2.4 SPARK PLUG ADAPTORS AND SPARK PLUGS
• Aircraft engines using 18mm & 1⁄2” reach spark plugs use adaptors with the same outside thread and a 14mm & 3⁄4” reach inside thread.
Use LSE high performance HP plugs, Denso spark plugs starting with a W or NGK spark plugs starting with a B in their designation.
• Aircraft engines using 18mm & 7/8” reach spark plugs use one of the following:
o LSE long reach adaptors with 12mm inside thread for Denso X27GPR-U
or X24GPR-U or equivalent 12mm spark plugs.
OR
o Optionally, for high performance applications, use LSE HP-LR (long reach) adaptors with 14mm inside thread for high performance HP-LR or IKH 14mm spark plugs.
• Install adaptors in cylinder head using the supplied copper washer. Torque to 35 - 45 ft-lbs using anti-seize compound.
• Install automotive style spark plugs with their washer. Torque to 20 ft-lbs using anti-seize compound.
PMAG CURRENT MANUAL ENTRY
Auto Spark Plug Adapters - Plug adapters permit the use
of 14mm automotive type plugs. Use short reach (SR)
adapters if your aviation plug callout is “M” type (for
example REMXXXX). Use long reach adapters (LR) if
your aviation plug callout is “B” type (REBXXXX). First,
install adapters with the supplied gasket on the spark plugs
finger tight. Then, insert the combined assembly (plug with adapter) in the engine and tighten to 18 ft/lb (standard auto plug torque) through the spark plug ONLY. Do not torque the adapter itself.
Note 1: If you install and torque the adapters separately, stresses will be focused at the adapter neck and can cause it to fail during installation.