They will be fine for a while if you keep them in small pots close together less than 2' from the light. Bunch them up like SOG, but make sure that under the canopy there's good air circulation so you don't get rot.
Here's a pic of what I use my extra MH 250 for... it's about 18" from the canopy, and illuminates 9 plants in 1 litre pots - the plants are from 10-16 inches tall and the taller ones get bent over a bit so the low leaves get more light.