I would not use the built-in PlantPax instructions. At all.
They are permanently constructed with no-access members, and therefore can never be optimized for efficient external access.
(There are placeholders for these datatypes in all 5580 and 5380 processors, so I've already had the opportunity to analyze these. And discuss the issue in my manual's application notes.)
The alternate method that FTLinx uses to assemble data blocks has limited buffer space, so won't help significantly on large applications.
Rockwell is shooting itself in the foot.