If you don't have time for cow/calves
You probably don't have time for many stockers unless they have been pre-conditioned.
In years past you could get by with the "do or die" system---- if you had lots of high quality pasture. All calves know how to eat grass- and with lots of room to spread out- load outbreaks are decreased.
And With the cheap gains you could afford to loose some calves along.
The high cost of calves means that you cannot afford to use the "do or die" approach and pencil out reliably.
So now its either go labor intensive for the first 60 days or go with preconditioned calves.
As far as gain--- thats hard to say
It depends mostly on how their nutritional needs are being surpassed.
And that can vary from one farm to the next.............
The ideal wt bought depends on your siituation-- If you have lots of high quality feed and room - and the time(handling and length of) and expertise to keep the "candy asses" alive. Go smaller and get more gain for your intitial investment.
Of course you have to factor in higher cost/lb of smaller calves; cost/lb of gain and interest and labor and roll over time .To see if extending time and going smaller is really worth it.
If you have limited feed inputs(quality or quantity)and time and expertise-- go with the 5-6 wts.
As far as selling the open market is a little stronger for the 7-8 wts. If you have a whole load you can market larger calves
private treaty.
My target wt to sell--- is when I see a good profit or I get the load sold to a buyer or I am running out of grass
If I had limited inputs and was just going for slow cheap "so-so pasture" gains- I would go with heiffers. If my goal was to put as much wt on as I could(without getting them fat) I would stick with steers.
There is no best breed for stockers--- some you sell cheaper but then you bought them cheaper too. Overall the balcks and baldies sell the best.
Greeenhorns should steer clear of excitable breeds.
As for pen size--and how to make use of it--- that really depends on what your goals are and the type of calf you buy and how many.