Homebrew PCBs

This afternoon I finally got around to mixing up a small batch of 
the 1/3 HCl + 2/3 H2O2. I've read the positive reviews on that recipe 
here, but was really surprised/impressed at the results.
     My usual initial test is to cut a small strip of .005" brass and 
wave the end around in the solution, and it dissolved in record time. So, 
I set up a sheet with some photoresist (laminated dry-film), burned my 
favorite test file into the resist, developed it and popped it into the 
beaker. I hesitate to say that it took minutes to etch, it would make 
more sense to describe it as seconds. Since the test file has two parts 
panels, I dropped the second one in and it was nicely finished in short 
order. The guy that craves these parts is going to be really pleased, as 
am I.

     Question:
     The solution total was about 225 ml, and the brass sheet was etched 
one sided with an etch area of a couple of square inches. Afterward the 
solution was quite hot and bubbling like soda pop on the stove. I put it 
in a cold water bath to cool it down, but I have to wonder - is there the 
possibility of a runaway reaction and what is the result?

     Oh, and I'm sure this is common knowledge to the rest of you, but on 
say, a 1 oz and 2 oz board, what are the copper thicknesses?

     Thanks,
     -Gary