This thread really helped me out and I wanted to point out that SOpAttach you select is the model attachment you'll try to use.
This may help find the available attachment points on any model: http://www.sc2mapster.com/forums/development/data/47592-where-to-find-model-attachments-now/
I ended up using one of the weapon attachment points, but I'm still trying to figure things out. At the moment the turret will bob with the vulture, but after attacking the turret no longer bobs. I'm also still hooking up the missiles to the turret instead of the vulture's front end. If anyone already knows what's left I'd appreciate any assistance instead of continuing trial and error.