That granted the CF doesn't fluxuate with temperature like ally. but if you think that it only moves in one direction it doesn't it will bloat the OTA as well as increase its length. now theres your problem what is the back of ota made of? and the focuser tube?
there was a really good youtube presentation on a guy with a 32" Relay cassigrain look for the link in the forums. now he shows where you need the Zero shift though careful design. and it didn't stop at the tube (he was using a CF truss setup) and a aluminium primary mirror box, but the link between the mirror box and primary mirror fixing was CF. Zero shift! and carbon fibre in the secondary-primary mirror tubing admittedly there was a series of lenses mounted within. If you want to go that extra mile you should have your odometer calibrated, no use saying ive gone the extra mile just because the odometer says so. whoops i had mini minor wheels on my tractor?!
oh and for a bit O info here is a little link for non belivers.
http://www.engineeringtoolbox.com/th...als-d_859.html