Tube flexure/collimation

I am currently in the process of building a "string scope". Last night I temporarily put together the entire telescope together and tested it's ability to hold alignment using a laser collimator. There was some movement (only about a millimeter or 2) in the dot (reflected off the secondary -- I did not have the primary in place).

My question is: how much movement is allowable? The scope is an 8" F6. Does someone know offhand how tollerant the secondary tilt is in an F6 system?

The final design will likely be a bit more rigid. Also, the 1-2MM movement resulted from using a 2" Howie Glattner laser collimator which is probably about 4x the weight of my heaviest EP and the dot movement resulted from moving down to about 15 degrees elevation -- I'm not going to do any critical observing at that elevation anyway.

Any info is appreciated.

Thanks

--Ian

Ian, I think that a little deflection is typical for any truss or string Dob. I see 1-2mm all the time from horizontal to zenith.
Floyd