CJ I have heard this "Once they get over that size, they require cooler higher DO waters and die." many times but the studies I have seen do not reflect that. The ones I have read indicate that HSB can do about as well as BG and LMB in ponds ( they all reached thermal max and/or DO critical level about the same time). One problem is the fight untill they die aspect of HSB which is more prone to occur in hot water. There is a tendancy in small ponds that HSB don't reach their max size potential but still may get to 8 lbs.

Can you direct me to any studies/info on the "Once they get over that size, they require cooler higher DO waters and die." ?

This is not a test but rather a search on my part to check the data to see for sure about the answer.