Big Buck, my comment was half joking as to your term "muscling up" which sounds kinda ridiculous. Now I may not know anything after direct marketing grass fed in the upper midwest for 13 years. Most folks here think I am a nut job. Just spoke with a friend in TX that finishes over 1000 head a year for a co-op and we talked about the management, carcasses, and genetics challenges of both places. Concepts are the same, but do not be fooled by those that have access to forage year round and expect their results, period. Also trying to supplement that quality of feed with preserved forage will bankrupt you. I thought this was not your first rodeo and you messed with deer? Therefore you should know what producing a shoe leather product is

You are barking up the wrong tree with Pieds in grass fed. Find one successful producer uses them. Your first thought of yield is a mistake as well. The qualities that made you buy Aubracs for are what will come through for you in the finished product. You need to just compliment it, not fight it. I get the feeling your mind is made up so I guess I am posting this for others. Producing extremely lean beef will be doing a huge dis-service to this industry that already has this problem. Grow an Aubrac cow herd if that suits your fancy and find a line bred Angus or Hereford bull to wrap up the consistency. With those two breeds you will have a good choice in older lines that should have the right growth curve and ability to hold meat quality through the rougher times.
Lastly with a small herd of 20 cows equals, 20 calves, 20 yearlings, and 20 coming 2 year olds. You will have your hands full with grazing management and marketing. Then all the BS that comes along with owning cows such as hay, pink eye, foot rot, and so on. Why in the heck do you want to mess with managing 3 way crosses and extra bulls and straws in such an endeavor? The dirty low down secret to this business is really a quality product, customer service, and proper PRICING. Your scientific breed cocktail don't mean that much to the bottom line. Simplicity is best and honestly that is all one needs to make good grass fed beef.
There ya go more free info...