I am in the process of getting the parts picked out to build a cab. I am wanting to use a flared port for this. I am on parts express site and they have Precision Sound link to calculate the proper port length. It gave a shorter length then winISd. Is this normal? I do not have winISd in front of me but it gave 6.xxx" long and this flared port calculator gave me total length of 5.07" long. Let me know what you think.