If your exhaust outtake is located at the top of the tent then you could possibly get away with your current fan blowing through or pulling from a filter mounted in th top, this is so long as you have enough passive intake as well, as in you should have at least double the area for passive intake as you have for your exhaust.
@seedlingstarter can grow any auto or photoperiod for that matter in his tent, sure short strains would help but are not necessary, main factor for keeping things small is limiting their root space thus limiting how big they can grow, now if one doesn't want to do that then as you mentioned lst,hst,cropping and the likes are your friend
Thanks mr sparkle I'm only looking to grow about 2 plants at a time. I've had many harvest out of PC cases none too great but were decent enough. I grow right now for fun until I can get good enough to keep it rolling. So I still buy herbs pretty regularly, though I do enjoy reaping the herbs I sowed. So compared to my PC that only had 17 inches height, once putting my cfl lighting in it came to maybe 14inches which i had to LST my plant to keep them from touching the light so I know I'll be fine with the 3 ft of height.