No, trying to get items to merge with the various polymorph effects. I hadn't tested Hellspawned Grace, yet, but the default Polymorph Self and Shapechange spells don't merge anything. I'm also revising them to merge everything as per Iznoghoud's old scripts on the vault.

Sorry, it's the PNP shifter.  I've tried a mix of the "package" form choices supplied by the class  (Revenant, Stag Beetle, Drow Warrior, Battle Devourer) - along with others that I've 'learned' in game  (various other Drow, Troll, Dire Bear).  I really first noticed it when fighting the various undead in the Hall of the Sleeping Kings (Undermountain level 1) when I had alot of trouble damaging them. After that I started paying attention to the log in other fights and saw that any opponent with Damage Reduction absorbed some of my damage regardless of the form or weapon that I used. Nameless Light and Enserric (picked up on that level) should pierce the DR of most opponents, especially the occasional drow who have dr 5/+1 (IIRC). 

I've tried shifting with a weapon equipped (thinking perhaps the weapon properties 'merge' with the form) and with one or both hands empty, equipping the weapon(s) once I've completed the shift. Nothing seems to work (at least consistently).

I also notice that sometimes when equipping  a weapon when shifted, the weapon properties show a new temporary 'on hit' property. I don't know if it's connected to the issue.

Is the concentration skill necessary for any of the shifter abilities?