I think I may have found whats causing my low-end problem. If you look at the picture the stuffing is covering the four cutouts on the brace. When I did this I thought this was a good thing because I could stuff the top chamber of the box and the brace would keep it from falling out,(I did this because I lined the box after it was built and could not reach the top. What a PITA) So I started to think.... well its not restricting air flow to the port but, is it restricting air flow to the top of the box? So I then entered my box design in Winisd and subtracted 2.1cubes from my 8.5cube design and the graph looks pretty close to the REW graphs. So needless to say I removed all the polyfil from the top and even went one futher. I lowered the tune from 17hz to 15.45hz and I can tell an improvement. I only listened at low volume (like -40) to some music for a little while but I could feel more vibrations than I could before at that volume. I also did not hear lower output from lowering the tune which I was worried about and is why I tuned higher when I built it. You can probly measure a (slight) difference in over all output but I dont hear one
Im still waiting for my BFD to get here and waiting to take measurements when it does. Thanks goes to SteveC for putting the stuffing idea in my head and I'll get some measurements posted soon so we can see the difference this has made.