The results are in:
I was concerned about trying something new for the family, so, I woke up early and did a test cook (Steak and Eggs for Breakfast...yeah baby).
The Tri Tip felt soft to the touch, but definitely not what I would call mushy at all.
After cooking to 140, resting, and slicing, I ended up with a very tender Tri Tip Roast. Definitely more tender than without using tenderizer. It reminds me of prime rib tenderness. If you consider that mushy....so be it.
Because I used a lot of soy in the marinade, along with seasoned Papaya tenderizer, I thought the meat was a bit too salty. My wife tasted it and said it was perfect.....what did I expect from a soy based marinade?
So, when I cook for the group this afternoon, I'll rub with some Sugar in the Raw brown sugar to balance out the salt.
1) Regardless of what the science says, marinade makes meat taste more moist and flavorful.
2) Regardless of what the science says, tenderizer makes Tri Tip even more tender, and zero mush even after two days in the marinade.