I don't think temps are going to affect stretching much if any, shov...looks like those fluoro's are nice and close..that will definitely keep them nice and bushy if you keep them as close as possible..

I'm doing a little expirament myself with my flowers..got that cool tube and the lamp's within 6 inches or so of the tops, and they don't seem to be stretching quite as bad as they were when it was like 17-19 inches..growth is picking up nicely since it's gotten closer.