Clearly no one wants to read a question that long so here are the simplified questions.
Question 1-would it be worth the money to increase the cutting size from 15x15 to 15x20 or is 15x15 good enough since i likely won't make aluminum parts bigger than that.(mostly opinion)
Question 2- What's a good level of rigidity for a machine made to mill mainly aluminum with high accuracy and hopefully no chatter? What should be the maximum amount of flex at the cutting tip with about a 10 lbs cutting load?
If you want all the details just read my first post. Thank You in advance.