More mixes

Technology question here. Is there a reason why the number of mixes is limited to 8? Am working on a show with six screens that rotate to 7 different positions and using six projectors through two TH2G. The angles are quite steep and it would have been really handly to have loads of mixes to assign rather than trying to keystone the layers individually. Also been having a bit of trouble with the limits of the keystone corners in the layers, which I never seem to have a problem with when doing mix keystoning. Would just be curious to know next time I run into this problem.

Cheers,

Kevin