Why wouldn't it allow it to bush it out? An auto flower is no different to a normal cannabis plant other than it will flower when it wants to not when you tell it to. I
The trelis can go on at any time really, it's purpose is normally to stop the stem growing upwards, but rather sideways, and as such big shoots will form.
That's the issue, as low as possible without damaging the plant i'd have thought, get it as spread out as fast as you can. As you say, you don't have the luxuary of letting it spread to your pleasure
Hey bro it will depend on ur hieght constrants...They vertigo will get over 2ft anyway...Yeah u have alittle before i would start to bend here under the trelis exp after the stress shes been under so far..JMO..GL..Wait maybe 2 weeks let her heal with no more nute burns and what not...Maybe do a flush on her do 2x water(exp....1 gallon pot use 2 gallons of water)..GL