Indeed it will hold the weight, things that you need to be 100% sure of is that there is no backlash in your mount. backlash ='s nastiness! Ive added a photo for you that has backlash in the Dec axis, I recently rebuilt the EQ6 full strip down and clean out and I am still just tweaking it so that it is perfect! but i didn't catch the backlash oh well.
With your guide camera you will always have tears and frustration because its just not made for the job, its not sensitive enough to pick faint stars.
What robin said is right though with the alignment of the scopes, but on a personal level I like to have them aligned up for the sole reason that i use the ED 80 with its large FOV as a finder scope as such.
One last thing, if there is any wind around, forget using the 10" combo! it will not work it is too heavy and the old eq6 struggles to keep it still!
just drop the ED 80 on it with a finder guider and take wide field happy snaps!