Omcaree....
Whilst I agree with the "should be at 5000 feet, you will of course have noticed that there is class A @ 4500, so with a 500 foot buffer entry was probably around 4000 as a maximum, which all begs the question was it the most ideal place to conduct aeros in the first place?
That said and and as was pointed out, you had the opportunity to take avoiding action precisley because you were doing what you were always taught, look out.
M