Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
Do it for them.
Not sure why i didn't ask them in the first place, assumed they'd just tell me to put it at whatever the stock crossover was at i guess. They got back to me relatively quick with this response.
yes, we do not recommend to go below 1.600Hz (at least 12dB, better 24) but as such a low crossover point, you need to keep in mind that the power load of the tweeter also needs to be lowered. In case you like it quite loud, a higher highpass filter at around 2.500Hz would be more appropriate.