well theres not much more to say i guess…
i just dont know how to set it up in renoise…
i guess it has something to do with how you set the LPB…
thanks…
Patternlength 70 or E0 (hex) 
edit: download my xrns-file package, most of the tracks are 7/8 or 7/4
hosted by Charly Linch: http://www.charlylinch.com/Benefit_of_the_Xrns.rar
setting LPB to a multiple of 7 will certainly help you fitting everything in the right measure
Depends on how many measures you want in a pattern and how many lines you want in a beat.
I’m a fan of 12 lines per 8th note, so a single bar of 7/8 would be an 84 line pattern with 12 lines per beat. Or, you could make a 2-bar pattern with 168 lines.
listened to mr snares lately? 
A pattern length of 56 will give you 7/8 .