Vegging Indicia's

Hi Guys,
Probably a silly question...lol...My grow room has about 5 feet head space with my 10 L Air pots.I there a ROUGH guide on how high the plant should be Vegged,or roughly how many weeks before the switch to 12/12 so they finish a nice size[not touching the light? I dont mind topping and LST and i will but just looking for a rough Guide please. Northern Lights for instance,or that type of medium size stocky plant?
Because when you buy NL seeds for instance,they say is a Med size plant,but how do you know if it DOUBLES in size when turned to 12/12,or more???
Cheers Guys.

Just think short with Indicas. Stretch is 2 times.

Probably pay to do a bit more research on your strain/breeder...riu is a good place to do that..
What type light are you using? Ventilation ect?
5ft clearance means there could be temp issues...
Maybe scrog might be more suited to a small space...i vegged my white widow for 3 weeks
But it is more indica dominant than nl...i wouldn't go more than 2 weeks...imo

Using a 400 hps,but the room is 7.5 feet long,using x2 passive vents,5''ruck and rhino.
Cheers Guys.

1. Indica
2. Don't use an apostrophe unless you know how to do so.
3. Most will stretch double. Some a bit more. My NL stretched double exactly.

If you have a cooled reflector you can get the plants a lot closer to it.

I'm with Trousers and Rings, count on at least doubling in size. I use MH the first week or two of flower to keep stretch to a minimum. Sativas are known to stretch 2-3 times their size. Also if your plant is leaning toward sativa phenos(longer internodes/skinnier leaf etc., you can expect to see a little more stretch.

Cheers Guys

I veg 2 months if that helps. mh/hps.. I grab some clones too.