will this help me save money?

ok, i've got 2 boxes & 2 85m3h fans. but i need a fan speed controller, instead of getting 2 fan speed controllers could i just get one thats intake/exhaust but have both fans on outake (with passive intake). but to do this i'd have to make a hole through conecting the boxes so they're the same box, ones flowering box, the others veg so i would need to make a light trap. i'm planning on drilling two holes the same size as the fan, at the bottom of the box, making a light trap out of tubing. would this work? would i be able to keep the temperature of both boxes the same baring in mind that one is bigger than the other.

oh yeah the fan controller has a digital temperature setting.

The veg box will get more hot than the flower box when flower time is around.

There is nothing wrong with trying it out. Just keep both temps monitored.

i dont know much, lol but u might wanna try switching the polarity on the exhaust fan or the other one that would not be in use,if all it does is spin the motor the otheer way