The elevator travel on my Avistar was off when I checked it out-of-the box. I was getting 9mm of up travel, which is perfect, but 15 of down! How can I fix this? The elavator is flush with the stab, too.Thanks!

If your elevator is at neutral with no stick input and zero trim, then the difference is probably just a result of the geometry of the control horn and pushrod setup. I really wouldn't worry about it. You shouldn't be giving it full elevator travel while flying anyway, and it's better to have more than you need than to run out of elevator when you need it (inverted and approaching the ground ).

You should be fine.

Make sure the servo horn is at 90 degrees when stick is centered.
Make sure holes in the control horn are centered on the hinge line.

straight and normal flight you won't use much down any way. maybe none. Inverted usually takes some but for a trainer... well I wouldn't worry about too much down. as i say you might not even use down elev.

Do the 90 and 90, first
If you have a computerize TX, you can adjust the expo only on one side of the the throw if you wish.