advise on controlling height of 3 sativas in 2x4 tent (5 feet height)

Hi Guys, I'm starting a grow and I now have 1 royal flush fem (old seed I had) and 2 Jock Horror fem, both strains are from Nirvana, I started the royal flush a bit earlier, that one is starting its 4th node, the 2 jocks are a bit more than 1 week old and have 2 nodes I think. I grow in a 4x2 tent that is 5 feet tall with a 600w MH/HPS in soil.

I'm currently hesitating on how to go about controlling the height of the plants. Some options I think would be to:
-top the plants say twice so that I have 4 tops on each plant
-mainline the 3 plants so that they have 8 tops each

Basically I'm trying to find out if mainlining the 3 plants will give me too many tops for my space... and thus resulting in smaller colas.

I'm also considering mainlining the Royal flush (that is ahead of the other 2), and topping once or twice the jocks.

Anyways any advise appreiciated

Well, 1st off you picked the wrong strains for a 5' tall tent, and mainlining. The reason I say this is because your plants are probably going to run into your light, as they are BIG plants, they take a long time to finish, like 10 weeks easy, more like 12, and if you mainline (I don't care for it much) , you will add another week or 2 for recovery of the plant, as it slows it down big time from finish. You have to top those plants, and even then they will grow tall. Next time choose a Sativa/ Indica mix, focusing on a dominant Indica, which speeds up finish time and be easier to manage in a tent. If you top the plants twice, which I also dont recommend because every time you do that, it will slow the plant down even further and that's probably going to be an issue for you, as I'm pretty sure you want to smoke as soon as possible. So, I would top once, and get ready for some training, like maybe HST, because you don't have a lot of room it seems.

As far as lost time caused by topping or mainlining I dont really mind it if I lose a few weeks. I was initially thinking to plan so that the plant doubles ones I enduce flowering, do you think I should plan for the plant to tripple instead? Yeah I agree for the strains, next time I'll go with something a bit easier to grow I think

I am very new to this stuff, but in a pinch just let them get somewhat rootbound and that MIGHT stunt them enough. Not great for the plant though id imagine.

OP I didn't research strain but if sativa dom like Jim said, you will challenged vertically. Planned final pot size? I say 3gal max. With that space lucky to top once without crowding, maybe super cropping if and when needed. You can crop past mid flower with healthy plants, a nice failsafe. And flip to flower before any get more than, say a foot tall

if anyone's interested, heres the grow journal i started

https://www.rollitup.org/t/royal-flush-and-jock-horror-fem-from-nirvana.929847/

I had the exact same setup. Some plants respond well to manifolding, others not so much. On my last run (3 plants in 3g pots) I manifolded a gth #1 and a MLxBD. The haze loved it and I pulled 120g off the plant. MLBD was only 60g, not great for a long veg.
Use tomato cages to help keep things in order and super crop until the end of stretch and you have them at the height you want. Your light will be st the top of the tent pretty quick.
Defoliate and lollipop heavily by Day 11. That's my little rule. Make sure to defoliate the Centre of the tomato cage to let light and air through to the lower buds in the colas. Get rid of the really small stuff all the way to the bottom.
Have little fans above and below the canopy.
After two runs like this I upgraded my tent to a 3x3x6 and it's SO much easier/cleaner. 4 plants.
Best of luck.

Why don't you try some low stress training? I have limited hight for my grow so I LST my plants, it's a bit time consuming if you have a lot of plants but with a small grow it's not that bad. Apparently it will also increase your yield, if I had the space I would've liked to test it and see. I find low stress training to be a good way to keep the plants short without stunting them.

I can top, LST, and bend and keep a sativa at 3', but if they are already 5' might be late at topping, certainly would not hesitate to do it at 5' if heigth was going to cause problems.

Just squish the stems and bend them over, maybe tie them down and try to keep them all the same height.Heres a batch of 90% sativa 3 weeks in flower picture taken today. Trust me on this, if you do not snap the stem, 1-2 days later they will look perfect.

You have to keep agresssive with them and need to do some training every 2-3 days for like a 3-4 week period. These are about 30" tall and 3 weeks into flower, might get another 6" on then, all bud length.

Hard work all done,