I've been doing a LOT of research into the Philippine Division photos yet I'm yet to find any?
Yet I see a LOT of reenactors wearing them? The pre-war regulation is the division patches are for wear on service coats and field jackets but, not shirts. I have LOTS of photos of regular U.S. Army Divisions not wearing patches on their shirts pre-war as well.
So, I'd say DON'T wear them unless on a field jacket... what say ya'll?
I think the confusion and gray area about patches come from the multiple goals of different type of reenactment activities. It's not always black and white.
If doing a "tactical" with no audience, just a straight "simulation" then it's preferred that the patch is not worn for additional suspension of disbelief.
If a particular event's aim is "torch bearing" like living history displays and "to represent" at reunions and educating the public, some of us opt to wear them. The goal is different. It's for "torch bearing" purposes.
There was an older lady who approached me one time at the Reading, PA WW2 Weekend. Out of hundreds of WW2 reenactors, she noticed that I was wearing a Phil. Div patch. I was the only guy in the whole event portraying the PS. She came to me and had tears in her eyes. She said her dad was a Scout and she didn't expect anyone to be representing them at the event, but there I was. If I hadn't worn the patch, I wouldn't have touched the heart and honor this daughter of a Scout. For this event, the goal of the impression was "to represent". In this case I'd rather wear the patch a'la "postwar." The happiness I brought her was worth it.
(postwar practice of wearing patch on shirt)
Another example was when a PS vet approached one of the guys at the Mt. Samat ceremony and touched his Phil. Dept patch fondly. He said he wished he had one as a keepsake. In this case the patch clearly evoked a fond memory for the veteran and made him happy. Wearing the patch was worth it.
On the other hand, let's say a high budget movie is going to be filmed and authenticity is a high priority, I say do away with the patch and so on... In such a case, the movie audience would most likely know that the soldiers in the scenes are Scouts, and so on.
But ultimately it's the preference of the reenactment group as long as they know what is authentic or not, balanced with what the goal of a particular event is.