Let us know what that does to your humidity.
What's your entire set up? I was running at 78-84 with my 1000 MH. I have a scrubber that sits at the bottom of the tent and I routed 4" ducting from the output to right over the tops. I left enough ducting so that it's adjustable. With that, I'm running right at 72-78 now.
Common sense is telling me that since the scrubber is at the bottom it's pulling cool air up to around 3/4 the height of my tent, it mixes with the hot air and lowers overall temps including what's getting vented out the top.
I guess all I'm saying is that from what I've seen, you could probably do a fan, whatever size, rigged up at the bottom with ducting that exhausts at the mid-top of the room and get the same result. Cold air falls, hot air rises... mix it all together... lol
All in all I think you did a great job here to meet your needs. I always like seeing home grown gadgets... I have a few too.
Was just thinking, I'd throw some rock salt in there and get that thing a solid block of ice. Probably last a little longer.