I'd suggest starting with 25 CX and seeing how that goes. That's significantly more than 11, and will give you experience dealing with a larger batch of chicks. Then after that batch is finished, evaluate your process, change as needed, and then do a batch of 50 chickens. The gap between caring for 11 vs. 25 CX is IMO greater than the gap between caring for 25 vs 50 chickens. The impact of poo management alone from 11 to 25 is significant. 25 chickens is usually where you get your first reduction in price per chick when ordering in bulk, and 25 chickens is the minimum order amount for most hatcheries that sell large volumes of chicks (and therefore have the best prices).
I found that 25 chickens was the limit that I, as one person with a full-time job, could reasonably care for, manage, and butcher by myself, with my current time limitations and setup. I butchered from 5-9 weeks, hand plucked 7 whole chickens, and skinned/parted out the rest. Since my family cooks and eats chicken 4-8 times a month, 21 chickens (that made it to butchering) will last us 3-6 months.
Working up to large batches of CX is generally recommended because if something goes wrong, you lose less chickens (and less money) than when doing a really large batch.
There are as many different processing setups as there are people using them. If you search on this site and look at the Sticky resources, and check out youtube, after a while you'll get the general ideas of how a setup works. But what works best for you is really what you need to find out, and that's something you have to figure out on your own, probably with some trial and error.
Also a note about selling processed chickens. Be sure you check your state department of agriculture for the laws surrounding home/farm processed chickens - there are as many differences in these laws as there are states in the USA it seems like. Depending on the laws, commercial sales may or may not be economically feasible for you in the volume you are talking about in the location where you live. It's very worthwhile to run a whole cost estimate for your process, to look at all the costs and income from your proposed operation, including licensing fees, inspections, certifications, feed costs, bedding, predator protection, labor, etc. and see if you can make that work for your target price per processed chicken. There are a number of threads on here about the challenges related to small chicken processing operations, and how folks have dealt with those. It can be difficult to turn a profit unless you can balance all the factors just right.
Good luck!!!