Need Advice on Clones

So I have an opportunity to pick up 20 clones that are about 10" high. They guy that has them has no room for them and needs to get rid of them. I have the room in my small grow room but how can I keep them small until I transplant to the great outdoors in Mid to late May?? They are Indica but not sure what strain. I have always started from seed around February and this has worked for me. Not sure if the clones will work... Also, the clones this guy grows is known for the best weed in my area. Lastly my maximum height for my room is 3'.
Thanks in advance for the help!

Get the biggest pits ya can find and train the fuckers hard lst supercrop top fimm u name it you ll av to do it all to keep em that low its gonna be a mess but who cares aslong as u got wot ya wanted!!

Pinch the tops now. Let them grow a bunch of new shoots. Take cuttings. Once cuttings take, throw those old bitches out.

judicious pruning will keep them compact until then

Keep your light as close as possible, [that will limit stretch]
and use the minimum wattage lights [that will limit over all growth]...
And play with a couple of them...
Once you get to the 8th node, top it,
and cut it back to the four biggest branches...
Sounds like fun...