I know on my dads fullsize chevy we have a single 3/8 port bag, it is fast enough for what I do with it, I have some friends that have a single 1/2 and it is alot faster but there is not much play in the middle, it is ether all the way up or all the way down, hard to hit it just right in the middle. The only people that I have heard of using dual ports are people that want to hop. that way they can get a ton of air in the bags really fast, but if that is not what you want to do i think you would be happy with just a single port. I have only heard of bags with dual 3/8s or dual 1/2s not one of each, for me it would just be easier to go with a single 1/2 then you would have 1/2 in and 1/2 out.