If you don't mind me tossing another hunk of advice at you, do yourself a favor and skip the home made scrubber if keeping a low profile is truly important to you. Keeping smell under control is hard enough with a commercially built unit. Stealth is never something to cut corners on. If you go with the home grown scrubber, you'll almost certainly need to oversize it enough that, all said and done, you'll spend the money anyhow and will still have an inferior product.
Take it from someone who was where you're at now on the learning curve of running a personal grow op, There is almost nothing you can build that will do the job as well (or at all) as just biting the bullet and saving up the cash for the proper piece of equipment when it comes to lighting/atmosphere control. Sucks, I know, but I spent plenty of bad money learning that lesson. Other more experienced growers will be through here that will agree with this sentiment.
Either way you go it's fun to grow weed. This place is a good resource for growers, All for the low price of free, too.
good luck keep us posted!