Hempy transfer to soil ?

I have been looking for information about this. I pretty much figure it is ok in the first 2-3 weeks and I have read some people say on here that they have transferred to soil... BUT I am not sure how long (or large) I can go without having problems. Right now they are 12 days in and in solo cups.
The idea was to take advantage of faster early growth and develop a good set of roots... Then transfer to some larger smart pots and let them finish outdoors.
anyone ever done this?

Thanks
DD

Easy as going from bubble cloner to 4 inch pot ...in one go ...yeah I use seedling mix, as your roots have been doing other things lately, best not to risk nute burn so early but pot up to 3 gallon in 2-3 weeks and the roots will be more accommodating to potting mix, use dim light for the first day, in seedling mix, reduce any shock,

Ok. Thanks. Good advice. What about how big you let them get in the hempy? You think something Like about 4-5weeks with normal growth ok?