I didn't see a topic for Other Caliber Lowers, so I apologize if this doesn't belong here.

Are the mag well drop-in conversion kits for converting a standard AR to a 9mm reliable?

I have a standard lower that already is an SBR lower and the price is obviously more attractive to temporarily convert it - but is it really that simple? I know the best answer is to just get a dedicated 9mm lower and another tax stamp, but I'd like to avoid all of that AND a new upper if possible.