Actually, when I heard that PAHL might be considering making a change along the lines of eliminating more body checking, I did a bunch of research about it. Most of the research on this has been conducted, unsurprisingly, by Canadian universities. This quote is from one of the studies I found (and yes, I admit it's just one study, but their findings were typical):
"It has been posited that learning to body check at a younger age might somehow protect players from injuries related to body checking at older ages. The literature, however, does not support this (McPherson, Rothman & Howard, 2006). A further comparison between Bantam minor hockey players from Quebec (no previous body checking experience) and Alberta (2 years of body checking experience) revealed a similar rate of injury in both groups in their first year of Bantam (Emery and Kang et al., 2011; McLaughlin, 2011). In addition, the rates of injury for the Bantam players in Quebec were similar to those of the Alberta players in their first year of body checking, suggesting that regardless of when body checking is introduced there will be a spike in injuries sustained. In a breakdown of injuries sustained, there was no difference between the groups in terms of concussions, severe injury or severe concussions. Contrary to common misconceptions, introducing body checking at an older age (Bantam) when players are larger, faster, and size discrepancies may be greater does not result in significantly increased rates of injury nor does it result in more severe injury."
Both set of emphases were bold in the original text. Note that, at the time the report was produced, PeeWees were permitted to body check in Alberta, but in Quebec body checking started at Bantams. The full report is available here: https://www.hockeycalgary.ca/assets/file/BC Final Report.pdf
Now, in my my heart I actually agree with the logic that starting body checking earlier makes for more prepared players, as I argued above, but it appears from the data that injuries as a whole are not affected by starting earlier (or later, for that matter). I admit that I find these results entirely non-intuitive, but that's what the report prepared for Hockey Calgary found from the data. It's a complex issue. I honestly can't help but wonder if my own beliefs on this are skewed entirely by my experiences and biases on it.