Update (Aug 4):
I decided to bump the DVD POT ALL the way back up to the factory level, as opposed to only raising it partially, as I had done in the interim.
My goal being to maximize laser lifespan, to avoid (hopefully) ever having to open the console up again.
I assume the weaker laser power, due to the higher POT, won't strain the rest of the drive mechanism when it comes to reading DVD+R DL backups.
In any case, everything seems to be loading as fast as before.
Hopefully the following specific feedback will help some others who wonder whether or not to bother with the POT tweak, which is definitely no longer needed WHEN using GaryOPA FW 1.3:
I increased the DVD POT on my Hitachi 47DJ back up to stock level (4.01 to be exact, which is essentially the same as the original 4.03).
The games (burned at 2.4X and even 4X) all still boot fine, with NO tricks needed.
Here is my setup:
Burner: Pioneer DVR-111D with TDB 1.23 fw.
Media: Verbatim DVD+R DL media ID = MKM00_ (_ = ?)
Burn speeds used: 2.4X and 4X.
(I was initially tempted to buy the Fuji's on sale at BB, that someone just reported success with, but the Verbatim dye is supposed to be good for long term reliability).
Xbox 360 DVD-ROM = Hitachi 47DJ with GaryOPA 1.3 fw.
I hope this helps a few others with questions.
Thanks for the feedback!