Additional Ad-Hoc lighting

Hi guys. Just joined. Great site. I have a 400w metal halide which i'm using for flowering (not ideal i know). So far i've been vegging on the window sill hoping for a good summer but gonna swap to cfl's....i'm on a budget. My question is could I supplement the window ledge veg stage with 4, 8 or 12 under the MH to give them a boost? Weather here's been pretty crap and I'm getting spindly little girls. Would the random(ish) timing under the MH cause flowering/hermi probs? Any comments? Keep up the good work fellahs.
Rufus.

Hi Rufus, welcome to RIU.

Yes. That's not good. No. ... Will do.

i put from window to under lights all the time,do it with everything,they love it,i just make sure i keep my veg hours around 18,doesnt mind whether sun or cfl,or your 400.good luck.

many thanks Trapper. I'll give it a whirl.
Thanks for the welcome y'all.