If you want to make a good line array, my suggestion is;

1. Don't use RD75
2. Don't replicate the concept of the XRT2K

Here is a collection of line array pictures found in cyberspace,
some are commercial line arrays, many are DIY, and only a few
are good designs. Study the pictures and send me an email and
I'll give you one opinion on which ones to get inspired by.
http://home.pacbell.net/lordpk/speaker/

/hehe