Nice speakers Phil-G did you build the 828 cabs ?
My 828 cabs are quite rustic ( where used in a movie theater and then by a disc jokey), need to fix the up nicely one day. Does the sub blend in well at 80hz? I somehow got the notion in my head that I either had to cross lower ( i.e. where the 515/828 combo starts to fall off naturally ) or higher ( to meet the 828 front horns). But I will try different possibilities with minidsp and possibly go for a better quality active xover later.