Purple pakistan chitral is probably not the most suitable strain for SCROG indoors, but if you love the strain maybe is worth to try. I'd recommend you Tikal, Congo, Panama or even the most sativa Orient Express phenos for a SCROG indoor grow.
I actually decided im going to top my PP plants at the 5th or 6th internode, and I remember reading that PP has relatively low vigor, so how long after I top would you recommend that I flip to flower?
Let always couple of weeks minimum after trimming to develop new tips and big enough to hold the floral buds. Switiching too fast to 12/12 after trim may produce lower yield and this line is not a big yielder although not particulary slow on growing new tips so that way can work great.