OF course, poly-framed pistols flex more than steel-framed pistols. One of the benefits of that flexing is the absorption of recoil pulse. Yes, some of the earliest Glocks with rails did have problems with lights attached. That's been corrected.
I guess my question to the OP would be, "If you had all of that data, the math of which is probably above your head, as you admitted, what would you do with that data?"
The old "steel is for firearms, plastic is for toys" mantra is pre-adolescent silliness or just plain ol' ignorance.