You say box mod, but I think you mean bottom FEEDER. There are many different types of box mods and bottom feeders out there. Yes, I know language, learning the language is a beach :0)
If your considering trying a BOTTOM feeder, you can't beat the Old Goats. Sturdy little buggers for 20 bucks (that includes shipping by the way) and then you can decide if you LIKE bottom feeders. I HEAR they aren't for everyone but what do I know

) it's all I run! If you do like the Old Goat, then you can step up to some of the fancier feeders like a Reo or a Hog.
Just my 2 cents!