This is probably not what you are looking for, but I have seen optiflex used in a big feed yard.
The first time I ever heard of optiflex was close to ten yrs ago. The feed lot that I was working at part time split about 5 pens ( may be 250 hd each) into two groups as they were reimplanting, the first through the chute went to the right and the gate was swung and the second to the left- 3rd tothe right --ect. Then they fed one half optiflex and not the other half. I got to see the end results after harvest, the half fed optiflex was just a very small bit better on gain, conversion, backfat, and and rib eye --- BUT--- 15% to 30% less choice and primes than their mates not fed optiflex. The manager told me that was the end of that and it was kind of a test through the company that sold optiflex.
Years later, this lot sold to new owners and one morning I was sent to bring a pen up to be shipped out ( which I normally did not do). I could not believe how bad these cattle walked and seemed stiff and slow. I asked one of the guys if there was some thing wrong with these or if this was normal for feed lot cattle in hard frozen pens or something. He didnt seem to know or care and several weeks later, I over heard one of the feeders asking for the pen numbers that were going to be fed optiflex, I inquired if the pen I followed up was fed optiflex-- and they were.
Any how - this is my experience with optiflex and some are comparing it with zilmax which I have no plans of using either one