I would transplant the rooted clones directly into the 1.5 gallon pots and skip the plastic cup altogether. this will just save you quite a bit of time, as you know transplanting is a lot of work. There is no specific time for transplanting other than you want to get them transplanted before they become root-bound. You will know when they are because growth will begin to slow and after a while it will stop. You want to avoid this point, as it stresses out your plant. Good luck and respect to you