The red just means the BFD is close to clipping the signal....it's not optimal if it goes much beyond that...sort of the final warning. I would just turn the volume on the sub up a bit, and manually decrease the sub level in the receiver's settings a bit to compensate.

Rich, setting filters is a iterative process. Set your first 2 filters (starting low to high) and then measure again, you may find some other frequencies outside the target range were affected...especially multiples of the frequency in question.

When you get really brave with it you can use it to boost your subs lower frequencies a bit to compensate for where it starts to roll off. It's sort of cheating but it's a great little perk to this thing.