Yeah, I don't see why not - that being said, the more lights, the more efficient it is and the more even the lighting is throughout the canopy - better to have more small lights than fewer large lights, all else equal.
I got rid of my 1Ks when I designed my new setup, so I can't take any light readings for you, but if you can get light readings off of a vertical bulb, I can give you the dimensions of both my 4" base setup and my new 3" base setup and you can work from there - that being said, I'd recommend the 3" base if only use the (1) 1K bulb - however, if I was gonna run 4 1Ks vertically in my cooltube, I'd have stayed with the larger 4" base diameter.
If you're handy at all, there are a lot more options open to you - if I knew when I started what I know now, I'd definitely do a fair number of things differently (and save lots of money).
Kdog, you're about a half year late on your recommendation.
Had 10 clones in the system for the past couple of days and they didn't die, so I filled that motherfucker up today - have lights 1 & 3 (from the bottom) on at 75% intensity, so 900 total watts going.
76F, 63% RH, CO2 @400-600PPMs, 5.5pH, 300PPMs.
Some of the clones are better than others, so I'm hoping for a two week veg before I start flowering - still debating whether or not to be a screen in there..........decisions, decisions.
EDIT: took pics today but want to wait to make sure all the clones live before I post them :)