First time hydro

Heya! I wouldn't do that especially in hydro as it can quickly lead to plant deficiencies. Typically they say to flip when you're at half your desired height as it will stretch significantly through the beginning weeks of 12-12. Another thing you could try is before flower, tie all the branches down to make the plant shorter. Good luck and cheers!

Cutting back on nutrients in a hydro setup will lead in deficiencies in no time! Not a good idea! Unhealthy plants will give weak buds and are prone to diseases, Cutting back on vedge time or starting 12-12 from seeds will give you smaller plants.

Next time, flower a couple of weeks earlier. - Or, only do one plant, and top it to fill the entire space. You'll probably get the same yield as two plants anyway.