My plan for the AV15 is 250 liters tuned to 20 Hz. Question 1: I'm trying to decide between two 4-inch flared ports and one straight PVC 6-inch port (no aeroports, no MDF roundover). Any comments one way or the other? I realize that a single 6-inch port has more area than dual 4-inchers, but I'm wondering if the flares on the 4-inchers more than make up for that. Question 2: I'm using the published T/S specs. Does anyone have measured T/S values for the DVC AV-15 in series? Question 3: I've configured LspCAD's "filter" settings in the box utility to emulate the PE 300-794 250W plate amp that I'll be using for power. Does "Active 2nd order highpass, 18 Hz cutoff, Q of .71" correctly describe the 300-794's rumble filter? Question 4: I'm really fond of the smooth, seamless character of my EBS shiva. Am I going to lose some of that by tuning this AV-15 higher? (I wanted to tune higher to get rid of the "trough" just above tuning that you see in many EBS alignments). Question 5: I've built some full-range cabinets and a sonosub, but never a "box" sub. This will be a big box. Any helpful hints or rules of thumb for how much bracing will be required (maximum panel span between braces or whatever)? Can I get by with .75" walls and 1.5" baffle, or should I go thicker? Here are the LspCAD graphs, the first pair is modeled for 1W, the second pair is modeled for 250W. I have enabled "simulate port nonlinearity", which explains why the F3 of the 1W graphs is 21 Hz, and the F3 of the 250W graphs is 29.5 Hz. It also explains the funny looking cone excursion graph on the 250W graph. 1 Watt... 250 Watts... Thanks for your input and advice!