Yes, thank you for your efforts ... I know gelatin blocks are expensive , and messy to make if you go that route . But The PPU results seem to be an outlier in the grand scheme of things ... did you happen to shoot more than one shot? I am not a fan of PPU, I like the Hornady XTP's so this is not an attempt to defend the PPU but consider this
http://www.americanrifleman.org/articles/2015/4/16/throwback-thursday-the-fbi-ammo-tests/
What is important here in this chart is the average penetration depth verses the success rate .. The average penetration was based on shots against bare gel, clothing protected gel, and auto body sheet metal gel, ect ( eight categories/ combinations described in the article)... the success column was the percentage that penetrated more than 12 inches ..
You can look at some of the 45 acp that had an average over 13 inches and yet only half penetrated over 12 inch and even the 380 penetrating less than 7 inches on average had 20 percent penetrate over 12 .. that screams VARIABILITY .. YES YES YES odds are your tests show average penetration , life is a bell curve after all.... and I know you probably spent more than you should have, and I am not knocking the test, they are much appreciated , In fact I respect the heck out of you for actually doing the work ... please don't misunderstand... I'm just saying I wouldn't expect very many PPU to penetrate like that if more shots could have been fired. To do the FBI test they used 24 tons of Gel.
So if you have PPU .. don't throw them away... Just buy my favorite XTP next time

and truth be told, I prefer XTP's, mostly because I can buy them for reloading and at a price not unsimilar to FMJ. So I am thinking value with them more than better anything, and I still prefer FMJ for barriers, not because I have some super faith in some exceptional lethality above and beyond any other bullet design we are talking a ~1000 fps < 100 grain bullet here .. physics allows only so much.
Sorry, had to interrupt my post ... anyway to wrap this up .. another point made is that only 20% of police fried shots actually hit the target.. the article asks , in light of that fact.. how much concern should we give the chance of an over penetration? You have to know and clear your background.. or be willing to accept the consequences of a miss, much less an over penetration.
Another good article that can inform this discussion
http://www.gunthorp.com/Terminal Ballistics as viewed in a morgue.htm