LED Bag Seed Grow

Hey guys this is my second grow, but first indoor grow. I'm currently growing 20 plants from seeds. I have them all in solo cups and was wondering if I could avoid transplanting them into larger pots (2gals) until I am able to determine their sex? It will be easier if i can just toss out the males and transplant the females due to my small grow area.

Is there anyway to force the plants into pre-flowering? They have started to grow 7-Leaf fans (and stank a little) and were planted in Mid/Early May they range from 10''-18'' I'll try to get some pics up after work

Grow Info:
-Bag Seeds
-90W Cree LED UFO Light
-2x 65W 7000 Lumen CCFL's
-18 Soil plants
-2 Hydro Plants