No prob:jointsmile: I'm no expert, so I hope some others will chime in.

I ran my setup like you for the same reason, hoping not to overheat the fan. Check the ratings on those fans... Whichever one has the better temp rating, then use that. Mine was rated for up to 75C I believe. If they are not high enough in your mind, then at least make it a straight shot, with the fan next to the light blowing through it and straight out the closet. Since I rearranged, it feels like there is double the airflow of hot air out of my box when the lights on.

There is a grow log here I just saw where a guy had similar night temps, and I believe it will slow down growth, but I dont think they will die with those temps,. Maybe a small heater that has a thermostat could go inside your box, that way its most efficient, and you won't have to turn it on and off (or get another 24 hour timer like the one for your lights). Plus you could then use this setup year-round. It's either that, or find another place in your house for this box. My night temps are about 22-23C, still within range, but I dont keep any inline or exhaust fans on. I only keep the small computer fan blowing on the tops.

And finally, a bigger box is easier to cool and fit more things into, like a carbon scrubber or the heater, ect.. Also, making it easy to water the plants and flush the plants if needed. Right now my soil buckets sit on top of a screen on top of other buckets, so excess water can drain.

Oh yeah, about the watering, they need to get pretty dry between watering. I water once every three days with some run-off within the first couple hours that the light turns on, but that's just me.