roll your burps and imp rise will keep the amp out of protect. do you have the stock alt in still? if so, you do not have nearly enough electrical for .5ohm. definitely need to upgrade that 4awg to 1/0awg. i mean, why restrict current? 45* along every edge is not ideal. you want them in a way to shoot air out of the port, not just throw it around and keep it out of corners. some times 45*s hurt your score. and a 45* is not a brace.
droping a class is up to you. NEVER just say "it's ok, trust me". i cant tell you how many times i have said that, or seen some one say that and they were VERY wrong. so measure the port and tell us the dimensions. if you're right, you're right. if you are wrong, we can catch it.